Sybase PowerDesigner Vs Erwin

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A Comprehensive Analysis of Sybase® PowerDesigner® 16.0 InformationArchitect vs. CA ERwin Data Modeler r8.1 Standard Edition

tABle of Contents 1 Product Overviews

1 CA ERwin r8.1 Data Modeler2 Sybase PowerDesigner 16.0

3 Data Modeling Activities 3 Overview5 Types of Data Model 6 Design Layers7 Managing the SAM-LDM Relationship10 Forward and Reverse Engineering10 Summary10 Integrating Data Models with Requirements and Processes11 Generating Object-oriented Models11 Dependency Analysis16 Model Comparisons and Merges17 Update Flows

18 Required Features for a Data Modeling Tool18 Core Modeling26 Collaboration29 Interfaces & Integration

39 Adding Value to Data Modeling39 Managing Models as a Project40 Dependency Matrices

41 Conclusions 41 Acknowledgements 41 Bibliography 41 About the Author

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introduCtionData modeling is more than just database design, because data doesn’t just exist in databases. Data does not

exist in isolation, it is created, managed and consumed by business processes, and those business processes are implemented using a variety of applications and technologies. To truly understand and manage our data, and the impact of changes to that data, we need to manage more than just models of data in databases. We need support for different types of data models, and for managing the relationships between data and the rest of the organization. When you need to manage a data center across the enterprise, integrating with a wider set of business and technology activities is critical to success. For this reason, this review will use the InformationArchitect version of Sybase PowerDesigner rather than their DataArchitect version. If all you need to do is create data models for an individual database, it is recommended you seek the cheapest tool or one that suits your specific technical deployment needs. However, when you are connecting data models to components of the broader architecture, I encourage you to read on to understand how CA ERwin compares to PowerDesigner InformationArchitect.

In this review, I examine the capabilities provided by CA ERwin Data Modeler r8.1 Standard Edition, and Sybase PowerDesigner 16.0 InformationArchitect, using the evaluation editions available on each company’s web site. The PowerDesigner evaluation software provides the full capabilities, including a repository. The CA ERwin Data Modeler evaluation provides a limited set of capabilities — the Standard edition, which does not include the repository capability.

produCt overviewsSybase PowerDesigner and CA ERwin Data Modeler are two of the market-leading data modeling tools available.

Both enable you to create different types of data models, and link those data models to each other. Both enable you to reverse-engineer databases, to persist the design in a model, and generate changes to the database. Both tools provide a drawing canvas, and a variety of editing facilities for use in expanding the detail of the model. They also provide standard usability features such as undo/redo, and the ability to customize the style of your diagrams. They both allow you to share the information held in your models via reports, though only one provides a web portal. They both provide essential collaborative features such as a repository.

However, when you look more deeply into how these features are delivered, you’ll see that ERwin does not come close to matching the breadth and depth of capability provided by PowerDesigner.

CA ERwin r8.1 Data ModelerOn their web site, CA describes ERwin Data Modeler as “an industry-leading data modeling solution that provides

a simple, visual interface to manage your complex data environment”. Before the release of r7, the predecessor to r8, ERwin focused completely on the development of tightly-coupled pairs of logical and physical data models. Each ERwin file can contain one logical data model, one physical data model, or one of each. A file that appears to contain two models actually contains a single model with two views, logical and physical. In r7, ERwin introduced the concept of design layers, a simple mechanism that gives hope to those of us who believe that the world of the data modeler is more complex than just matched pairs of logical and physical data models. Look at the next section to find out more about design layers in ERwin.

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ERwin has several editions and additional components:

Data Modeler Standard Edition

Core data modeling tool, providing logical and physical data modeling capabilities

Data Modeler Workgroup Edition

This combines the Data Modeler Standard Edition with a repository to support workgroup collaboration and governance.

Metadata Integration Wizard

An OEM feature built into ERwin, to convert to and from the formats used by other tools, including most of their major competitors (including PowerDesigner)

Data Modeler Navigator Edition

A read-only version of the Workgroup EditionSeparately licensed component

Data Modeler Community Edition

A free version of ERwin. The tool features are restricted, and the largest model it can manage is one with 25 entities/tables.

Data Modeler Validator

Verifies the structural integrity of data models or SQL/DDL code. Separately licensed component

In addition, CA can bundle ERwin Data Modeler with OEM products for extracting ERP metadata and for data profiling. Both products are also available on the open market, and can integrate with other data modeling tools, including PowerDesigner. To trial ERwin, just complete a form on the CA web site and the file will be downloaded. The downloaded file is called ‘ERwin.exe’, so be careful if you’ve downloaded previous versions. The Model Validator requires another registration and a separate download.

The evaluation license is valid for 14 days from the date of installation. Once the evaluation license has expired, the evaluation version reverts to the Data Modeler Community Edition. If you do need temporary read-only access to models, I suggest you download the trial version of the Data Modeler Navigator Edition of ERwin, which will give you access for 14 days.

When my evaluation license expired, a UK reseller provided me with a one month extension.

Sybase PowerDesigner 16.0Sybase PowerDesigner is a single tool, combining several standard modeling techniques (full lifecycle data

modeling, data movement modeling, business process modeling, enterprise architecture, and UML). PowerDesigner provides a single working environment, underpinned by a flexible architecture and their industry-renowned Link and Sync capabilities, the key to the comprehensive impact analysis capabilities of PowerDesigner.

Downloading and installing the evaluation version of PowerDesigner was simple, and I only had to register once for all available components. If you want to avoid involving DBAs in creating and managing a repository database for your evaluation, you can host the repository database locally, using a specially licensed (free) version of Sybase SQL Anywhere. You can also install the PowerDesigner Web Portal locally, allowing you to quickly create a complete test environment. Some organizations choose to continue using Sybase SQL Anywhere to host their production repository.

Once the evaluation license has expired, you may contact the Sybase sales department for extensions. You may also register and download the freely distributable PowerDesigner Viewer software, for read-only access to any of your models on the file system and/or in the repository you built.

PowerDesigner is available in several editions, illustrated in Figure 1.

Data Architect/DM Core data modeling tool, providing logical and physical data modeling capabilities, and the dedicated XML model

Data Architect/RE The core data modeling capabilities, plus the collaborative capabilities made possible by the repository, the web portal, and web-based authoring

InformationArchitect Extends Data Architect/RE to provide additional capabilities for managing information architecture

Enterprise Architect Extends the InformationArchitect edition to provide additional capabilities for enterprise architects

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figure 1. PowerDesigner editions

dAtA modeling ACtivities

OverviewThis section examines the support provided by each tool for the key activities involved in the creation and

management of a chain of data models. In a later section, I examine some of the key features a data modeling tool must provide in order to make these activities efficient, effective and productive.

The chain of data models is illustrated in Figure 2, using a PowerDesigner Business Process Model. Each box in Figure 2 represents a fundamental data modeling activity. The other icons represent inputs and outputs to and from those activities, most of which are data models.

The overall flow of activities represents a top-down modeling approach, though I expect all data modeling tools to provide bi-directional support for each flow, and possibly support flows I haven’t shown, such as generating a Relational PDM directly from a Business Subject Area Model.

There are three types of data models in Figure 2:• Subject Area Model — Represents a business need. It is a very broad view, containing only the basic and critical

concepts for a given scope. The Business Subject Area Model (BSAM) is a subject area model of a defined portion of the business (not an application). There are other possible types of subject area models, but the modeling principles are the same, so examining support for the BSAM will be sufficient.

• Logical Data Model — Represents a detailed business solution, capturing the business requirements without complicating the model with implementation concerns such as software and hardware.

• Physical Data Model — Represents a detailed technical solution. It loses some of the exactness of the LDM, but this loss usually comes with gains in performance and usability within a given hardware and software set.

In Figure 2, the <<stereotype>> notation identifies the type of PowerDesigner data model that would be created in each case:

<<CDM>> Conceptual Data Model

<<LDM>> Logical Data Model

<<PDM>> Physical Data Model

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figure 2. Data modeling activities

ERwin and PowerDesigner both provide support for all of the activities shown in Figure 2. However the effort required, the user experience, and the resulting impact analysis capabilities are dramatically different.

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SuMMARy MATRIx OF THE DATA MODELINg ACTIVITIES DEPICTED IN FIguRE 1

Task/Product ERwin PowerDesigner

Creation of a multi-level data architecture

One tool is used to create three levels of data models with ERwin’s Design Layer Architecture. Though they are not specifically clear, the steps you would take are:• Create the SAM as a logical model, where

you just ignore unwanted features, such as keys and attributes (if you choose to)

• Derive the logical model from the SAM, in a new file

• Amend the LDM• Derive one or more PDMs from the LDMSee “Managing the SAM-LDM Relationship” on page 7 for more.

One tool is used to create all three level of data model; each level is supported by a separate and distinct purpose-designed type of data model.The steps you would follow are:• Create the SAM in the CDM• Generate the LDM from the CDM• Amend the LDM• Generate one or more PDMs from the LDM

Impact Analysis for a multi-level data architecture

Impact Analysis is fragmented. Each derived model has a reference to the model from which it was derived, but this is the only record of the derivation visible in ERwin. The ‘where used’ information for an entity or table will not tell you anything about dependencies on other models. The real dependencies between model levels are invisible to the modeler, though they must be recorded somewhere within the derived model, as the synchronization process matches renamed objects.

Impact and Lineage Analysis provides a continuous trail, from SAM to LDM to PDM(s), which can be interrogated from any point, in any direction. The ‘where used’ information for a SAM entity, for example, will show the trail of dependencies through the LDM and PDM(s), and any other associated models. Additionally, PowerDesigner provides a function to create an updateable graphic (i.e. model) which depicts the Impact and Lineage Analysis.The dependencies between models can be shown on a project diagram, an Impact Analysis Diagram and/or via the Generation Links function.

Types of Data Model Based upon this overview of typical Data Modeling Activities, it is necessary to align and integrate business

analysis with technology implementations to fully model a complete system. Where data modeling is concerned, an organization must create subject area models, logical data models and physical data models.

A Subject Area Model (SAM) is a “set of symbols and text representing the key concepts and rules binding these key concepts for a specific business or application scope” (Hoberman, Data Modeling Made Simple, 2009). It is commonly expressed in the form of an entity-relationship diagram; however it is purely data and relationships. It is not relational — a SAM does not require foreign-key constraints.

A SAM helps us to capture, understand, and analyze the business needs of an organization, business area or application from a data perspective. It is completely devoid of implementation details (data storage structures) or software constraints. A key component of a SAM may be a set of elementary business data element definitions, which may or may not have any eventual existence as modeled objects. PowerDesigner provides support for data elements in the form of data items in the Conceptual Data Model (CDM). ERwin does not provide any support for data elements. See “Support for Elementary Data Elements” on page 24 for more on this subject.

One or more SAMs may be created prior to developing the Logical Data Model (LDM) for a new application. A SAM might also be created for an existing system where the technology needs to be verified with the business.

PowerDesigner’s CDM is designed for creating a SAM; ERwin can only support the SAM by ignoring capabilities in a logical model, by pretending that a LDM is in fact a SAM.

A Logical Data Model (LDM) extends the concepts described in a SAM, describing a potential solution. The modeler must be able to generate a LDM from the SAM. At first glance, the LDM is quite similar to the CDM in terms of the objects it contains. However, a SAM is allowed to contain unanswered questions, such as those represented by many-to-many relationships — these questions must be answered in a LDM. Entities must have primary and foreign keys, and many-to-many relationships must be converted into entities.

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The Physical Data Model (PDM) would typically be generated from the LDM. This model will be used to design the schema of the database that will be used for the system. Entities become tables, attributes become table columns and the relationships will be implemented in the database-specific structures (referential integrity, stored procedures). When creating or generating a PDM, the specific database is chosen (Oracle 11i, Sybase ASE 15, Microsoft SQL Server 2008, PostgreSQL 8, etc). The PDM is frequently used to generate the data definition language (DDL) that will allow for database creation or modification. It may also be used to create or update database schemas via a direct database connection.

Again, the LDM and the PDM appear similar, but they meet different needs, and differ in terms of the detail provided. The LDM is used to explore domain concepts with the business stakeholders; the PDM is used to create and maintain the database. Multiple PDMs can be generated from a single LDM — this can be useful for database migrations, the creation of production and development databases, or application migrations.

Both tools allow you to generate multiple PDMs from a single LDM, and maintain the links from LDM to PDM, though there are limitations in ERwin that don’t affect users of PowerDesigner, which you can read about in “Dependency Analysis” on page 11.

Design LayersA modeling tool should provide the ability to model at any level, with generation to the other model levels or types.

All artifacts should be linked to their corresponding objects in the other models (for example, the entity “Customer” in the SAM should be linked to the “Customer” entity in the LDM, which is linked to the “Customer” table in the PDM). All linkages should be maintained in the modeling tool so that a proposed change in an object can be analyzed before it is changed. It is essential that the linkages form a single unbroken chain.

The activities described so far have all been based on “top-down” analysis and design. In reality, data modelers often use a hybrid approach, combining both “bottom-up” and “top-down”, so the tool must be able to support the generation of a SAM or LDM from a PDM, and the generation of a SAM from a LDM. Both tools have this capability, but the support provided by PowerDesigner is superior, due to the explicit support for all three types of data model, and the loose coupling of data models.

ERwinHistorically, ERwin users have worked with tightly-coupled logical and physical data models. In this environment,

changes in the logical model are automatically reflected in the PDM (and there can only be one PDM). ERwin’s Data Modeler r7 introduced the ‘design layers’ functionality, which allows you to derive one model from another, maintaining linked models in separate files for the first time. So you can derive a LDM from a LDM, and a PDM from a LDM, creating the chain of models shown in Figure 2. You can also work upwards, deriving a LDM from a PDM. You do have to be careful when synchronizing a model with the model it was derived from — the default comparison options don’t include all the properties you may need to compare, such as attribute and column data types.

I did have an issue with the design layers feature in ERwin. My LDM includes two many-to-many relationships that I hadn’t resolved. When I created a new PDM, the many-to-many references were still present. ERwin allows you to use a transformation to resolve many-to-many relationships, but only in the LDM. In my evaluation edition, transformations weren’t available to me, though the help information indicated that they should be. To resolve the relationship manually, I wanted to copy one of the existing entries, which I did by selecting the entity on the diagram, and using standard copy & paste. The new entity was not allowed on the diagram, as it had the same name as the original entity. A look at the browser confirmed this — I had two entities called ‘Phone’. When I renamed the new entity to ‘Contact Phone’, it appeared on the diagram. No damage done, but I didn’t expect to be allowed to create duplicate entities. If you don’t like this default behavior, you can change it via the model naming options.

My original model had been imported from a PowerDesigner CDM, and I was eventually able to carry out transformations once I had added a new entity or relationship to the model. I raised this with the product team at CA, who were able to import the PowerDesigner model without these restrictions.

The physical limitations of the storage structures would typically be included in the PDM, such as which tablespace, the size of the tablespace, how many rows are anticipated, etc.

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PowerDesignerPowerDesigner extends the two types of model provided by ERwin, to include a dedicated CDM, Object-oriented

models, and XML models. In addition, you can generate almost any type of model from almost anything else. Figure 3 shows the generation links available for data models. You can see the flexibility this gives you, with a model designed to manage a SAM, and three different types of model to support physical data modeling.

figure 3. Generation, import and export options for data models

When generating a new model, you can be selective about which objects to generate from in the original model. A detailed record is kept of the links between models, and between objects in those models. This information is available for carrying out impact analysis, and is also used to ensure that models stay synchronized, where necessary.

Sybase refers to these capabilities as ‘Link and Sync’.

SummaryERwin provides great support for tightly-coupled logical and physical data models, and merging models together

(via the sync facility), but it cannot compete with the additional model types provided by PowerDesigner, nor with PowerDesigner’s link and sync technology.

Managing the SAM-LDM RelationshipI used a realistic scenario to examine the support for integration of the SAM and LDM in each product — using an

existing LDM to form the basis for a new SAM. The CDM was then amended, by hiding or removing the foreign key attributes, and drawing a many-to-many relationship. I would then attempt to document business rules and stewards, and link them to the entities in my SAM.

How well does each tool support the SAM and links from the SAM to the LDM?

ERwinCreating the SAM was easy to achieve, by deriving a new LDM from the original LDM. The next task is to make the

new model look more like a real SAM. The many-to-many relationship was not a problem, ERwin allowed me to draw it OK. Hiding foreign keys, though? Not possible. Removing foreign keys? OK, I can do that, but only by removing all attributes from the primary keys, and creating unique alternate keys for any candidate key attributes I want to keep. I can’t remove the primary keys or convert them to alternate keys, so I have to keep them.

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This task took much longer than I expected it to, due to one of the idiosyncrasies of ERwin. If I double-click on an entity symbol, it opens the entity properties, which doesn’t provide access to the details of identifiers or attributes. I have to close that dialogue (can’t have more than one property editor open at a time), right-click the entity symbol, and select ‘key groups’ to amend the primary key and create the alternate key.

In ERwin, I was able to remove attributes from all the primary keys, but there was one inherited attribute that would not go away, in the ‘Person’ entity shown in Figure 4. To remove it, I had to detach the ‘Person’ entity from the subtype symbol, and then re-attach it.

figure 4. An unwanted PK attribute in ERwin

I would like to document business rules and stewards, and link them to the entities in my SAM, but I can’t do that in ERwin, except by creating a User-defined property to hold the name of a business rule or steward, which would have to be defined elsewhere.

The ERwin Design Layers options allowed me to synchronize the two models. The links between the models were not visible from the SAM I created.

PowerDesignerIn PowerDesigner, I created the CDM by generating it from the LDM, making sure that generation dependencies

were created. These links can be viewed from both ends, within individual objects and at model level.CDM doesn’t migrate attributes along relationships, so there are no foreign keys to remove. All the primary

identifiers can be removed very easily. If for some reason I decided to use the PowerDesigner LDM as a SAM, removing foreign keys would involve two quick steps. In step 1, open a list of identifiers, select them all, click on the ‘primary identifier’ property, and then click on <OK>. Figure 5 shows this dialogue in PowerDesigner, after the ‘primary identifier’ properties have been unchecked. All the primary identifiers have been converted into alternate identifiers.

figure 5. PowerDesigner list of identifiers

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In step 2, create a list report containing relationship joins, making sure to include the ‘child attribute’ properties in the content. Again, select all the entries, and amend the value of ‘child attribute’ to ‘None’, as shown in Figure 6. All your migrated attributes will be removed from the model.

figure 6. PowerDesigner Relationship Joins

In PowerDesigner, business rules can be defined in any model, or shared via the glossary which is held in the repository. You can then link them to any object you want to.

In PowerDesigner, most dependencies between objects are pre-defined and named. Any additional links you create are called Traceability Links, and you can assign a user-defined link type to each link. These link types can be presented separately in an object’s properties, filtered in lists of dependencies, and also displayed in dependency matrices.

In PowerDesigner, a steward would be represented by an organization unit in the business process model. There is not a direct link from an organization unit to an entity, but creating one is a trivial task.

figure 7. PowerDesigner entity with two new properties

Figure 7 shows an entity symbol, displaying two new properties that I added to the entity. One property is called ‘Steward’, and links the entity to the organization unit called ‘CRM Department’ in a process model. Populating this property automatically creates a dependency between the two models, which can be shown on a project diagram, and interrogated via impact and lineage analysis. The ‘Steward’ property can also be displayed in dependency matrices (see “Dependency Matrices” on page 55).

It is not possible to enhance models this way in ERwin.

SummaryERwin allows you to create a SAM based on a LDM, but the new SAM is still a LDM at heart, ‘pretending’ to be a

SAM. This pretense relies on ignoring standard LDM features, some of which (such as primary identifiers) cannot be removed. The linkages between the SAM and LDM can be maintained via the Design Layers options, but full visibility of those linkages is not available.

PowerDesigner provides a dedicated Conceptual Data Model, perfect for a SAM. When this model is generated from a SAM, individual LDM objects are linked to their corresponding objects in the CDM. These links are visible from within both models. The models can be synchronized in either direction using the standard model generation feature.

See also “Dependency Analysis” on page 11.

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Forward and Reverse EngineeringThe PDM can be used to generate a database creation script or can be used to directly create the database through

an ODBC, JDBC and/or direct connection to the database server. This is known as forward engineering. Generating a PDM from the structure of a database schema or DDL file is called reverse engineering; this may also be used to describe the generation of a SAM or LDM from a PDM.

Every data modeling tool needs to provide reverse and forward engineering. Many organizations find it useful to reverse engineer an existing system, generating a LDM and SAM from the PDM, so they gain a better understanding of the database and the applications that use it.

Both tools examined here support forward engineering, see “Database Support” on page 18.

ERwinERwin supports reverse engineering from either a database or a script file. When reverse engineering, the newly

created model can be either a physical model or a logical/physical model (in accordance with ERwin terminology — the logical/physical model is actually a single saved file that has diagrams for both logical and physical models). Template selection is provided and the process is wizard-driven. ERwin can attempt to infer keys (primary and foreign) based on the schema of the incoming database.

PowerDesignerPowerDesigner supports reverse engineering from either a database or a script file. Live database connection is

through an ODBC/JDBC connection with all objects supported. Script file reverse engineering is fully supported as well. Object inference is supported if chosen through the reverse engineering options. As with all data model creation modes, templates are supported for the reverse engineering. When reverse engineering from a live database, the database statistics can also be included (i.e., number of distinct values in a column, average length of a character field). Additionally, the statistics can be reverse engineered into a model without changing any of the objects. Reverse engineering is wizard driven.

If a LDM is also required, this can be generated from the new PDM.

SummaryThere is little to choose between the products here; your choice of tool may be driven by the DBMS versions you

need to support — see “Database Support” on page 18.

Round-trip EngineeringThe tool must also allow the modeler to reverse-engineer a database schema into a PDM, amend the PDM, and

then update the database from the PDM. This is known as round-trip engineering.A data modeling tool MUST support both round-trip engineering and the hybrid approach described earlier.

Whether a modeler is starting from a conceptual model or reverse engineering a database into a physical model, a tool is useless unless it can support all aspects. Other features might be “nice to have” but this is baseline functionality.

SummaryOf the tools considered for this paper, only PowerDesigner provides full support for round-trip engineering as well

as giving the modeler the ability to work forwards or backwards (e.g., start from LDM, create CDM and PDM from the LDM), and provide comprehensive analysis of the dependencies between all the models in the chain. PowerDesigner has conceptual, logical and physical data modeling all in one tool. With all data modeling aspects in one tool, coupled with PowerDesigner’s link and sync technology, the organization has the utmost flexibility in building, analyzing, and maintaining data-oriented systems.

Integrating Data Models with Requirements and ProcessesWhen a data modeler receives requirements or specifications from a business unit, the first step is to create

a subject area model (SAM). In many cases, there are also defined business rules, requirements documents, and business process models. Ideally, the SAM should be tied to the process model so that the stakeholders within the organization would have an understanding of the data and its use to support the processes. This also ensures that data elements used in a system are necessary. There are many existing systems and applications that carry data that is never used. The entities in the SAM can also be linked to the associated business rules, and requirements imported from documentation.

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ERwinERwin Data Modeler does not support process modeling or business rules. There used to be a separate tool called

ERwin Process Modeler, which was capable of synchronizing subject areas, entities and attributes with ERwin data models, but that product has been discontinued.

PowerDesignerIn PowerDesigner, the modeler is able to associate the subject area model with any process model that they have

access to. They can also link to any business rule in any model (not just data or process models) that they have access to. Via the glossary feature, they can also associate the subject area model with globally-shared business rules. Finally, requirements can be imported into a Requirements model from standard office documentation, and these requirements can be associated with any modeling artifact.

SummaryPowerDesigner is the clear winner here; the definition of requirements and business rules allows the modeler to

document far more than just what goes in a database.

generating Object-oriented ModelsAfter the SAM has been created, the next step would be to generate an appropriate model to begin development.

Within the scope of this paper, that model would be a logical data model (relational). It may be useful to create an object-oriented model from the SAM (PowerDesigner Enterprise Architect does this) but that is beyond the scope of this paper.

Dependency AnalysisThe very act of creating a data model creates dependencies between objects in that model, most of which will

be supported by the standard data modeling techniques, such as placing related attributes in the same entity, and creating relationships. When a new data model is generated or reverse-engineered from an existing data model, further dependencies are created. In addition, a data modeler may wish to create their own dependencies, such as linking data modeling objects to requirements, business rules or business processes, or even to other data model objects.

It is essential for a data modeling tool to allow the modeler (and others) to interrogate these dependencies — this may be called ‘impact analysis’, ‘where used’, or ‘impact and lineage analysis’. In the section below, I refer to this as ‘Model Lineage’.

In addition, there are dependencies between real-world applications, representing the movement of data between those applications. In the section below, I refer to this as ‘Data Lineage’.

Model LineageAt each step of the process, it is paramount for the data modeling tool to be able to show the lineage of the objects

in models. When examining the properties of a column in a table (in the PDM), the modeler should be able to see what attribute of what entity was used for its creation. The modeler should also be able to trace back to the reason the attribute was created, which may be to support a business rule, to meet a given requirement, or to implement a given data element.

This visibility and traceability helps to ensure that the organization uses only the data elements necessary for the implementation of a project or system. Furthermore, the understanding of where objects originate contributes to the proper business process implementation. The corollary to this full traceability is impact analysis.

Impact AnalysisImpact analysis, or the ability to understand the consequences of a model change, needs to be a function of the

modeling tool. As part of the impact analysis, a modeler needs to be able to understand the object’s model lineage).Impact analysis includes more than just understanding where an object is used. It is also important to understand

what happened to an object after it was generated. Was an attribute in a SAM generated into the LDM? Was it then generated into a PDM? Was the data type changed by the DBA when working on that PDM? Did a modeler generate a set of classes from the LDM so that the developers would be able to start building applications? It is useful to be able to store these analyses for later review as well as create version documentation. It is a better use of resources to intelligently discuss the proposed change with the stakeholders rather than make a change in the LDM, propagate it to the PDM and database only to find that the application now fails.

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The concept of impact analysis goes further when considering stored procedures or triggers that might have been created. If a modeler needs to change a data type or entity in the LDM, for example, an impact analysis would show if the object is being used in a stored procedure. With a proper modeling solution and discipline, the modeler would be able to have a discussion with the DBA prior to making the change.

ERwinERwin supports logical and physical data modeling, and allows you to pretend that a logical data model is a

conceptual data model, or SAM. Assuming you use the Design Layers model derivation process, the impact analysis available is minimal, limited to saving the results of synchronizing two models. It is not possible to trace the lineage of an object back from the PDM to the SAM, for example. You can use the standard “complete compare” feature to assess the links between models related by derivation, but you will not meet with much success due to the fact that you expect the SAM and LDM to be different. Merely renaming an entity in one of the models will fool “complete compare” into concluding that they are different entities.

ERwin has a “where used” function that will show exactly where an entity or attribute in the LDM is used in the PDM, if the PDM is in the same file as the LDM. Figure 8 shows the ‘where used’ tab for the LDM entity in ERwin; this tells you that the entity is linked to one relationship in the LDM, and that it appears on one diagram in the LDM. There is no information about the SAM from which this was derived, or the PDM that was derived from the LDM. One of the buttons on the toolbar under ‘where used’ allows you to edit the selected related object.

figure 8. ERwin Entity Editor — where used

In ERwin, you can only see dependencies within and between logical and physical data models, and they are only visible in the model in which they are defined.

PowerDesignerIn PowerDesigner, one tool provides support for all types of model. Any user can read any model (subject to

repository permissions/licensed package), and carry out full impact analysis in the tool, directly against the repository and/or via the PowerDesigner Portal.

PowerDesigner has true and extensive impact analysis. An object’s lineage is stored with the object. When models and documents are stored in the repository, the impact analysis becomes more extensive. While viewing an object’s properties, clicking the “Impact and Lineage Analysis” button will bring up a window similar to the one in Figure 10. The analysis results depend on the analysis rule sets you use. Rules sets allow you to tailor the impact analysis, determining the types of objects that are traversed in the impact analysis, and the properties that are displayed. There are several rule sets supplied, and you can create your own if you need them, and share them via the repository.

Not only is the impact analysis available for the data modeling functionality, but it is core to the tool, and is available throughout all modeling modules.

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PowerDesigner separates the concepts of ‘lineage’ and ‘impact’ to refer to the predecessors and successors of an object. Putting it simply, ‘Lineage’ refers to where the object came from, how it is defined, and ‘Impact’ refers to where it is used, those objects that will be affected if the object was changed or deleted.

For example, Figure 9 shows a chain of three data models. If we were to run Impact and Lineage analysis for the ‘Sample LDM’, links to the BSAM would be regarded as ‘Lineage’, and links to ‘Sample PDM’ would be regarded as ‘Impact’.

figure 9. Lineage vs. impact

By default, impact and lineage analysis only examines local models that are open, which could limit the scope of the analysis more than you would like. Just select the ‘Use Repository’ option, and PowerDesigner will extend the analysis into the repository. Figure 10 shows the impact and lineage analysis for the same ‘City’ entity shown in Figure 8. Note the wealth of additional information shown, and the inclusion of links to requirements, business rules, and classes. Entries with the small database symbol on their icon were retrieved from the repository.

figure 10. PowerDesigner impact and lineage analysis

Each of the entries provides a shortcut to the actual definition in a local model, and to a summary of the information held in the repository.

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PowerDesigner stores lineage and impact analysis information at both ‘ends’ of the relationship, which enables you to see dependencies from your model to other models that you’ve never seen before. For example, the LDM stores details of generated tables, and the PDM stores details of the entities that tables were generated from.

Impact Analysis ModelThe best way to fully appreciate the depth and breadth of the impact analysis capabilities of PowerDesigner is to

generate an impact analysis diagram. Did you notice the ‘Generate Diagram’ button in Figure 10? If you click on that button, PowerDesigner will generate a diagram illustrating the results of the analysis. The diagram can be saved, providing point-in-time snapshots through the development life cycle. Remember, you can choose between different analysis rule sets, which will produce different results and therefore different diagrams.

Figure 11 shows such a diagram, generated using the ‘conceptual impact analysis’ rule set and no lineage rules — this results in a smaller set of affected objects. The left-hand entry is the ‘City’ entity. The style of a symbol indicates the type of model that it comes from. Double-clicking a symbol will open the properties of that object.

figure 11. PowerDesigner impact and lineage analysis diagram

figure 12. PowerDesigner impact analysis model in browser

Look at Figure 12. It shows the entries in the browser for the Impact Analysis shown in Figure 3. This information can be saved as a model. If you have more than one Impact Analysis Model, you can compare them to see how the impact has changed over time.

SummaryWhere you have tightly-coupled logical and physical data models in a single file, ERwin’s “where used” capability is

up to the job. For any other circumstances, PowerDesigner’s impact and lineage analysis capabilities are far superior.

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Data LineageManaging the real-world movement of data between applications is an essential part of information management

in any organization. Knowledge of these data movements is probably documented in a variety of locations, such as ETL tools, web services registries, JCL jobs, and spreadsheets. In data modeling tools, this Data Lineage can be linked to physical data models, enabling anyone to trace the path taken by data through the organization.

ERwinERwin provides a facility for documenting simple data movements. You can create a data source in your PDM,

and populate it with tables imported from another model or SQL file. The columns in the imported tables can be linked to columns in your PDM, and you can add comments to describe the data movement, perhaps describing the selection logic.

There is no visual representation of the data source in ERwin; the link from the source tables to the PDM columns is only visible in the PDM column ‘data source’ tab, shown in Figure 13.

figure 13. ERwin data source

PowerDesignerIn PowerDesigner, this mapping process is much simpler. Just fire up the mapping editor, specify a name for the

data source, choose a model to map to, make sure that the option to create default mappings is selected, and then click on <OK>. Default mappings are created by matching object names and codes in the two models.

In Figure 14, I chose to map from my sample PDM to a PDM that I created by reverse-engineering the MS Access Northwind database. I have added some mappings between columns by dragging from left to right. The ‘Mappings’ window in Figure 14 shows the details of the mapping from the Person table to the Customers table; using the tabs, I can edit information about the mapping, such as the join criteria. All of the information shown in Figure 14 will be available through impact and lineage analysis and dependency matrices.

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figure 14. PowerDesigner mapping editor

In addition, PowerDesigner provides a dedicated model for data movements, which can import simple PDM-PDM mappings. The Data Movement Model is designed to manage data replication using Sybase Replication Server®, but it can be used to document other data movements as well.

SummaryERwin is great for capturing the context of an individual model, but it cannot compare with PowerDesigner’s

Mapping Editor or Data Movement Model. ERwin’s mappings are text-based, not graphical, and invisible from the perspective of the related model(s). In PowerDesigner, any mappings created can be viewed in the mapping editor, impact and lineage analysis, and via dependency matrices. They are treated in the same way as any other dependency between objects — they are visible and navigable.

Model Comparisons and MergesWhether a model is in a repository, the current workspace or saved in the file system, it will be necessary to

compare models and merge differences from one model to another. The modeler might be working on a particular entity in the LDM while another modeler would be working on the same model. Merge and compare functions help to contribute to the ability for an organization to perform collaborative modeling. All tools examined for this white paper contain merge and compare functions. The comparison operation is simply a visual representation of the difference between models. The merge function should allow a modeler to accept or reject any or all changes.

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ERwinERwin has a “Complete Compare” function. It will work with open models in the tool, script files and models, or

databases and models. Complete Compare is wizard-driven and allows the modeler to choose the “left” and “right” models. I like to be able to decide which model goes where, rather than leaving it up to the tool to decide. I would always have the ‘higher level’ model on the left; for example, a SAM on the left, and a LDM on the right. Once all selections are made in the wizard, the “resolve differences” dialog box is displayed, allowing you to decide which changes to apply, and in which direction. The merge is bi-directional.

You can mark ‘known differences’ to be ignored, save them for later, and apply them to future comparisons.The design layers feature also allows you to merge models in a limited fashion. You can add one or more model

sources, and choose the objects you want to copy across from those source models. Later, you can sync the target model with any of the source models; differences between the two models are presented in the same dialogue as used in “Complete Compare”. You do have to remember to save your sync options in a settings file, so you can use the same criteria each time you sync the models.

PowerDesignerThere are two techniques you can use to merge content between two models in PowerDesigner. You can use

the ‘merge model’ feature, which allows you to merge two model of the same type. Alternatively, you can choose to generate from the source to the target model in update mode, which gives the option of saving dependencies between the two models. Both of these features use comparison and merging functionality. It is part of the core function set of PowerDesigner and not specific to data modeling. This model merge function is invoked automatically (or can be invoked manually) when a model is saved to the repository, copied into the workspace where a model is already open, and when model generation is used to update an existing model.

PowerDesigner’s model merge provides fine levels of granularity and control as to what can be changed. Like ERwin, PowerDesigner allows you to manually match source and target objects in the comparison. In PowerDesigner, you can only merge models in one direction, from source to target. Uniquely, the PowerDesigner Portal provides the same comparison features as the client.

A feature unique to PowerDesigner is the ability to copy objects from one model, and paste them into another model as shortcuts to the original objects, or as managed replicas of those objects.

SummaryAs you would expect in two long-established products, the comparing and merging facilities are comprehensive.

Both tools have a single merge-compare operation, which can be invoked in several ways. They both allow you to choose the comparison criteria, filter the results, and save your selections for future use. Both tools allow you to document the comparison by generating a report.

ERwin has the edge in two respects, as they allow you to mark and save known differences, and the merge is bi-directional. PowerDesigner has the edge in its ability to generate and update more types of data model.

update FlowsThe boxes in Figure 15 represent the major components in an enterprise-level data modeling environment — these

are all supported by both products. Each dashed line in Figure 29 represents a possible flow of updates to models, either from modelers (experts in data modeling) or from Reviewers (who aren’t experts in data modeling). Again, all these update flows are supported by both products.

figure 15. Update flows

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In both tools, a standalone edition is available that only supports the data model component, and therefore only supports update access by modelers. In ERwin, that support is limited to logical and physical data models, and ‘pretend’ subject area models. PowerDesigner is available in several standalone editions, the most basic of which supports logical and physical data models, XML models, requirements models, impact analysis models, and ‘free models’, which provide a simple means of creating non-specific drawings and models. Conceptual and data movement models are available in the InformationArchitect edition.

The standalone editions may be sufficient for small organizations, but the majority would require an enterprise or repository edition. ERwin workgroup edition includes the repository. The PowerDesigner ‘RE’ editions allow access to the repository and web portal. The PowerDesigner web portal allows nominated users to input updates to text properties, such as entity definitions. These updates will be reviewed later by the model owners.

required feAtures for A dAtA modeling toolThis section examines some of the key features a data modeling tool must provide in order to perform the activities

described earlier, in an efficient, effective and productive manner. The features are grouped into the following categories: Core Modeling, Collaboration, Interfaces & Integration, and Usability.

Core Modeling

Database SupportSince one of the goals of using a modeling tool is to create, modify, understand and analyze databases, it is

necessary that the tool support a variety of DBMSes. Even more important is the ability for the user community to add additional database support without waiting for the vendor to provide an upgrade. This might be necessary when a system needs to be migrated from an older database to a more current solution, so the user can reverse-engineer the old database, generate and modify LDMs and SAMs, modify models, then create a new database. Consider a modeling tool that provides database definition files in an XML format so that additional database definition files can be created by the user.

To make this degree of customization possible, an intelligently designed modeling tool will be engineered so that the core executable reads definition files. The executable file is extensible, not only for different modeling modules (CDM, LDM, PDM, XML) but for database definition files. With a tool designed thusly, supported database updates can be released as soon as the database vendor makes the specifications available. The entire modeling tool does not have to be upgraded. Furthermore, with separate core and external definition files, it is possible for the customer to add support for a database not supported by the tool vendor.

PowerDesigner supports this paradigm while ERwin does not. PowerDesigner uses a single executable that is extended through DLLs for modules and XML definition files for all databases. Because of PowerDesigner’s architecture, it is possible to add support for a specific database system even if Sybase does not upgrade PowerDesigner to support it. The database definition files are stored in the file system as XML files and can be modified. ERwin does not provide this ability.

The following table summarizes the DBMS support provided by each tool. A “,” between version numbers indicates that different database definitions are used for the DBMS versions. If the separator is “-”, that indicates that a group of versions is managed by the same database definition. The “-” means that version-specific database support is not provided: a common set of attributes is supported.

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DATAbASE POWERDESIgNER 16 ERWIN R8.1

Adabas D Yes No

Allbase/SQL g.1 Yes No

ANSI Level 2 Yes No

Hitachi HiRDb No No

HP Neoview R2.4 No

IbM Db2 for AS/400 Yes No

IbM Db2 for z/OS formerly OS/390) 6.x, 7.x, 8.x, 9.x, 10x 8.1, 9.1

IbM Db2 for Common Server (aka LuW) 6.x, 7.x, 8.x, 9.0, 9.5, 9.7 9.1, 9.5, 9.7

IbM Db2 for i No 5.x/6.x

Informix SQL 8.x, 9.x, 10.x, 11.x 9.x/10.x/11.x

Ingres 3.0.1 2.5, 2.6, 2006

Interbase 5.x 5.x, 6.x 5.x

Microsoft Access 2000, 2007, 2010 2000, 2002, 2003

Microsoft SQL Server 2000, 2005, 2008, 2008 R2 2000, 2005, 2008

Microsoft Visual FoxPro No Yes

MySQL 4.0, 5.0 5.x

Netezza 4.5, 5.0 No

NonStop SQL Yes No

ODbC 3 2.0, 3.0

Oracle 8i2, 9i, 9i2, 10g, 10gR2, 11 10.x/11.x

PostgreSQL 7.3, 8 No

Progress No 9.x/10.x

Red brick Warehouse 6.2 5.x

SAS No Yes

Sybase SQL Anywhere® (previously Watcom SQL or Sybase ASA)

9, 10, 11, 12 No

Sybase AS Enterprise 12.0, 12.5, 12.5.1, 12.5.2, 12.5.3a, 15.0, 15.0.2, 15.5 12.5/15

Sybase AS IQ 12.5, 12.6, 12.7, 15.0-15.1,15.2 12.x

Sybase Avaki® Yes No

Teradata V2R5, V2R6 2.6, 12, 13

Both PowerDesigner and ERwin include support for all the database platforms listed above in every edition of the product.

When considering the database support that a tool offers, it is not enough to say that a particular database system is supported. For example, PowerDesigner supports all of the Oracle data types and nuances (storage, partitions) that are in Oracle 11g, including over 80 data types. ERwin supports fewer than 30 of the Oracle data types. If this is the level of support for a popular database (i.e., Oracle 11g), what might the support be for a less popular database?

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figure 16. Oracle data types in PowerDesigner

figure 17. Oracle data types in ERwin

As another example of the support offered by PowerDesigner for Oracle 11g, see the following figure.

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figure 18. Oracle physical options in PowerDesigner

PowerDesigner has all physical options on one tab. All Oracle 11g partition options are supported, as well as column properties, physical properties and all other options.

ERwin doesn’t present all the properties of an object in one dialogue. For example, Figure 19 shows the seven different dialogues available for tables. If the properties you need to read are not in the dialogue you have open, you must close it and open another (you can only have one open at a time).

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figure 19. ERwin Table menu

ERwin separates physical options from partitioning. There is no support for reference or system partition types.

figure 20. Oracle partitioning schemes in ERwin

SummaryThere is no doubt that the database support provided by ERwin meets the requirements of many data modelers.

The product probably supports the majority of features for the majority of DBMS versions in use. If your requirements stretch beyond the ‘majority’ in either respect, PowerDesigner is the product for you.

Modeling NotationThere are several different modeling notations commonly in use. A modeling tool should support more than

one notation.• Information Engineering — a standard notation in use in many tools, though there are several variations.

Generally, the entities and tables are represented by rectangles and the relationships are represented by lines with different endpoints, usually the popular “crow’s feet”.

• barker — created by Richard Barker and popularized by Oracle’s CASE tools, Barker notation displays inheritances inside the parent entity symbol, has its own multiplicity notation and attribute ornaments. Relationships are drawn in two parts with each reflecting the multiplicity of the associated entity role.

• IDEF1x — in this notation, each set of relationship symbols describes a combination of the optionality and cardinality of the entity next to it.

• Entity/Relationship — Sybase specific, Entity/Relationship is an implementation of IE notation.• Merise — developed as part of the Merise methodology, it uses complex multi-entity associations instead of

relationships.• E/R + Merise — both entity/relationship and Merise are used in the same model.

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NOTATION POWERDESIgNER ERWIN

Information Engineering (IE)Yes

(called Entity/Relationship) Yes

Barker Yes No

IDEF1X Yes Yes

Merise Yes No

IE + Merise Yes No

SummaryBoth products support two of the most commonly used notations, IE and IDEF1X, though there are differences in

the IE notation — ERwin uses dashed and solid lines to indicate whether or not a relationship is identifying, whereas PowerDesigner uses a triangular dependency symbol. If you want to use the Barker notation, or your organization uses the Merise methodology, PowerDesigner is your only choice.

Business GlossaryMany development projects and business re-engineering programs develop a glossary of terms, usually as a

spreadsheet. These terms may even form part of the naming standards for data models, but the majority of tools, such as ERwin, provide no support for this activity beyond the ability to record pairs of words to be used when translating between logical and physical names for data.

PowerDesigner provides support for a taxonomy of business terms via the repository-based Glossary. In environments with a repository, administrators can deploy a glossary of Terms: a Term is a word or phrase that forms part of a controlled vocabulary. In the ‘Naming Conventions’ section of Model Options, you can enable the use of the Glossary for auto-completion of names in any model. This also enables you to check the names of objects for compliance with the Terms in the glossary as part of the standard ‘check model’ feature.

If you enable the Glossary in a model, Terms are suggested from the Glossary as you type the name of an Object. If you type a recognized synonym for a Term, then PowerDesigner suggests you use the Term instead.

When you reference a term in the name of an object, PowerDesigner automatically adds that object to the list of objects that reference the term. This cross-reference is available in dependency matrices and impact analysis.

SummaryERwin does not support anything equivalent to the PowerDesigner Glossary. PowerDesigner is the only mainstream

data modeling tool to offer a shared, linked, glossary of terms.

XML is SpecialA physical data model describes data persisted in a database. In many cases, that data was transmitted to the

application that populated the database as an XML document or message. The structure and content of that document or message is a key component of the organization’s data integration, and must be included in impact analysis and data lineage capabilities. An enterprise data modeling tool should be able to create an XML-specific physical data model, in which the modeler can design the structure of one or more XML Schemas, and then generate XML schema files. The tool should also be able to import an existing XML Schema into a dedicated XML model, from which future versions of the schema can be generated. Only PowerDesigner has all this XML capability. ERwin can generate and reverse-engineer XML Schema, but it relies on a relational model to do so. The translation between a relational PDM and the essentially hierarchical nature of XML makes it difficult to effectively manage the development of XML Schemas in ERwin. The lack of a model dedicated to XML, with XML-specific objects, means that it is impossible to provide full, accurate impact analysis for XML schemas in ERwin.

SummaryERwin does not provide an XML-specific data model. PowerDesigner is the only mainstream data modeling tool to

offer a dedicated XML model.

Denormalization of physical data models It is vital for any data modeling tool to provide automated support for denormalization of physical data models,

including rollback capabilities.

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ERwinERwin supports rollups, rolldowns, horizontal and vertical splits, and column denormalization. Rolling up subtypes

into the supertype, and rolling down supertypes into subtypes, are supported by specific transformations.The Transforms toolbar provides access to the different types of transformations available, and also allows you

to display the objects before or after transformation. You can also reverse or resolve all transforms — resolving a transformation deletes the original objects.

PowerDesignerPowerDesigner supports table collapsing (rollup and rolldown), horizontal and vertical partitioning, and column

denormalization. You have the option to retain or delete the original tables. All transformations (except column denormalization) are recorded as transformation objects, linked to the newly-created objects. Via the model menu, you have access to a list of transformations.

Rollup and rolldown are supported by collapsing tables into a new table — you have the option to keep or remove the original tables. Rolling up and down super and sub types is best carried out in the LDM, using the options that govern the generation of supertype and subtype tables.

A transformation can be rolled back if the original tables were generated from another model — this does not re-instate the original tables, so you would need to re-generate them if you didn’t keep them when you carried out the transformation. If you think you will need to rollback a transformation, I suggest you keep the original tables and references, and uncheck the ‘Generate’ property to prevent them being generated into a database.

Column denormalization works by utilizing the standard replication feature — it replicates columns across tables. When the original column is updated, the replicas are also updated. The modeler has control over how strictly the copies mimic the original column.

SummaryThe tools both provide adequate support for denormalization. They take different approaches with respect to

managing the pre- and post- denormalization views of the model; if you are used to one approach, you need to be aware of the differences if you change tools.

Support for Elementary Data ElementsPreviously I introduced the concept of elementary business data elements, which may or may not have any eventual

existence as modeled objects.

PowerDesignerPowerDesigner supports this via the concept of Data Items in the CDM. A Data Item is a ‘conceptual’ data element

that exists independently of any model objects, such as Entities or Tables. Data Items are integral to the CDM, where every attribute automatically references an underlying Data Item. They are not present in the Logical Data Model or Physical Data Model.

ERwinERwin does not support elementary data elements.

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Other Core Features

CORE FEATuRE POWERDESIgNER 16.0 ERWIN R8.1

Enforce naming standards based on business vocabulary

Yes — using terms in the glossary

No

Record the vocabulary of the business as Terms

Yes No

Persist xML schemas as a model for traceability and normalization

Dedicated XML Model, or UML class model

XSD import not supported by evaluation edition — uses the same metadata bridge as ER/Studio, so it will produce the same result, a relational model

Check Model (validation) Yes — can customize checks, and determine criticality. Auto-fix available on some checks. Can access objects from results list without closing the list

Separate product (Data Model Validator) that appears to be comprehensive. It can read and validate DDL and ERwin models

I was unable to launch the validator from ERwin — I was informed that the DbMS in the model (Oracle 11g) is invalid. I was also unable to open the supplied sample eMovies ERwin model

Customizable Data Type mapping Yes — defined within the properties of the DBMS

Datatype Standards Editor — allows you to edit logical-physical and physical-physical data type mappings. Can save multiple versions, and attach to models. I haven’t seen any reference to DBMS-specific mappings, but I’m sure they must be managed somehow

Inter-Model generation & Synchronization

Yes LDM-PDM

PDM-PDM via model sources

Managed re-use of modeling patterns and reference models within data models

PowerDesigner library pushes reference models to all repository users

Partial — via model templates at the time of model creation

Multiple diagrams within a model Yes Yes

Naming standards (enforce/check) Yes — using the glossary Partial

Provide business name to implementation name translations

Yes Yes

Real-time updates of metadata Yes Yes

Replicate attributes between entities (ditto columns and tables)

Yes — see above No

Replicate objects between models Yes No

Shortcuts to objects in other models Yes No

Subject areas (subsets) in a model Yes Only 1 level

Support for elementary data elements Data Items in the CDM No

Automated support for denormalization of physical data models, including rollback capabilities

Yes Yes

Compare a data model with an existing data artifact such as an xML or database schema, update the model and/or the data artifact as a result

Yes Yes — databases only

Direct support for all model objects specific to a technology e.g. a specific RDbMS version

Yes No

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Core Feature POWERDESIgNER 16.0 ERWIN R8.1

Filter ‘Dangling Relationships’ from schema generation

Yes Yes

generate data definition language (DDL) files

Yes Yes

Multidimensional modeling Yes — No distinct notation Yes

Reverse engineer physical data models from data definition language (DDL) files or database connections

Yes Yes — some via Meta Wizard

xML schema generation Yes Yes

xML-specific physical data model Yes No

Configurable support for technology objects (e.g. creating generation capabilities for unsupported DbMS)

Yes No

Impact and lineage analysis between models

Yes Partial

Impact and lineage analysis within a model

Yes Partial

Visual editing and display of data lineage

Yes No

Compare two data models, of the same or different types, and update one or both models as a result

One-way update Yes

Collaboration

RepositoryIf there is going to be more than one person who will need access to a model, then a repository is necessary. The

repository provides a common location to store documents, models, and other files. It should be able to store different versions of models as well. From an administrative perspective, the repository provides the organization with a single storehouse for backup purposes. With proper use, the repository would hold the most current version of a model so that when a change needs to be enacted, there is no question as to where the proper model resides. Additionally, the repository would eliminate the necessity to locate the individual who might have a model locked or who might have implemented some changes.

A repository is necessary to support collaborative modeling, by managing versions of models. A database administrator may need to implement a change in a physical model, but, at the same time, a modeler needs to implement a change in the same model. Both people would be able to extract a copy of the model from the repository, make changes, and then put the model back into the repository. Upon storing the model back into the repository, the differences should be presented to the modeler consolidating the changes.

Both products are available with a repository.

PowerDesignerPowerDesigner implements full impact analysis through the repository, allowing you to trace dependencies through

models that you don’t have available locally. With all the models in the repository, it is much easier for the tool to track all the objects and be able to report to the modeler.

The “Model Merge” functionality discussed above is presented each time a model is consolidated into the repository. The changes between the version in the repository and the model being checked in are highlighted with the option to accept or reject any or all changes.

The repository presents in the tool browser as a folder-based structure. Security is implemented in the repository — users will have various permissions, based on roles. These permissions are defined by the repository administrator and are typically different from the database user permissions. Branching and sub-branching, versions, locks, freezes are all supported.

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The repository can be installed on a local Sybase SQL Anywhere database initially, avoiding the need to purchase disc space and involve DBAs until you’ve proved what you need. It can then be migrated to one of several supported database platforms.

ERwinThe repository for ERwin is the Model Manager, which provides the model management functionality for ERwin

Data Modeler Workgroup Edition.Model Manager provides library management, allowing for folder creation and better organization within the

repository. Sub-models are supported, not only through ERwin but also in Model Manager. ERwin Model Manager is more of a ‘model store’ than PowerDesigner’s repository; it does not push any information out to users, unlike the library feature in PowerDesigner; nor does it allow you to browse content using the client software or a web portal. CA supports version management in the Model Manager, including locked versions, difference reports, and model rollback to previous states. The Model Manager allows you to rollback to any point in the life of a model.

The repository is a database wherein the models are stored and managed. Users must check out models and check them in again, as in a standard version control system. Archiving and versioning are performed within the repository and the tools that are available to modelers are also available to work with models in the repository (e.g., Compare and Merge, Subject Areas, …). Security is implemented in the repository; users would have roles and privileges. Branching and sub-branching is supported.

CA suggests that you use the Model Manager in one of the following ways:

Model-Driven Development

Changes to the schema are made to the model first and then forward-engineered

System-Driven Models

Changes are made directly to the schema and the schema is reverse-engineered into the model to reflect the changes

Informational Models

Contains logical-only models, enterprise-wide models, or standards and sample models

The choice you make will influence the way you set up the repository database and the supporting policies. I haven’t had access to the Model Manager during this evaluation so I can’t be sure of the implications of this choice. In reality, you would probably want to use a repository in a hybrid fashion, combining all three approaches.

SummaryERwin’s repository offering is essential for multi-user environments. It is useful as a way of managing access to

models, and versions of models. However, it does not provide any direct access to repository content for modelers or non-modelers, unlike PowerDesigner, which allows modelers to browse the contents of models in the repository, and incorporate the repository in searches. Via the Web Portal, non-modelers can browse and search the PowerDesigner repository contents in the same way; and selected non-modelers can also (using the new ‘Composer’ license) update text properties directly in the repository.

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Web PortalA repository is essential for effective collaboration between modelers, and a web portal is essential for effective

collaboration with non-modelers.

PowerDesignerThe PowerDesigner web portal allows non-modelers to browse, search and compare models in a similar way to

users of the desktop software. The search facilities are actually better than those available on the desktop, and the impact analysis capabilities are comparable. Portal users have real-time access to the repository, so they know they’re viewing the latest checked-in models. The new ‘Composer’ license allows selected users to edit textual definitions via the portal (assuming you’ve granted them access to the models, of course).

ERwinERwin does not provide a web portal.

Other Collaboration Features

COLLAbORATION FEATuRE POWERDESIgNER 16.0 ERWIN R8.1

Compare versions of repository based models Can compare any version of any model to any version of any model of the same type

No

Manage configuration of different models that contribute to release

Yes No

Provide subscription for anyone to know when models are checked-in

Yes No

Impact and lineage analysis via repository Yes No

Projects and frameworks matrices Yes No

Share and apply a ‘house style’ for the appearance and content of data models

User profiles help you to standardize the look and feel of your models and to support standards

Themes

Share reference models and common business rules via a repository

Yes No

Direct access to models and links between models via a portal, designed for use by non-specialist users of data models

Yes No

Read-only access to models Viewer software is free Navigator edition — list price c. $1,000

Search and impact analysis capabilities via a portal, designed for use by non-specialist users of data models

Can search models, compare models, follow all traceability links and dependencies (impact analysis)

No

Web-based functionality at no additional cost to the repository

Yes No

A shared location for the storage of and control of access to data models

Repository — Enterprise license required

Repository — workgroup license required

Control access to subsets of a model, perhaps individual model objects

Yes — down to packages within models

Yes — down to submodels

Integrate with LDAP/Active Directory for user authentication

Yes Yes

Resolve potentially conflicting changes made by different analysts

Yes Yes

Role-based management of access to repository content

Yes Yes

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Interfaces & Integration

Import and ExportA modeling tool must allow the modeler to import and export content in various types of models and related

external files. Both import and export allow the tool to work with other tools or provide information to other people, organizations, or solutions. It is useful for the tool to be able to work with metadata in a generic fashion, but specific importing will provide greater overall support.

Both tools offer several import and export features.

ERwinERwin Data Architect includes an OEM Metadata Integration Wizard1, enabling users to export and import to and

from many other formats.The ERwin Bulk Editor is a single window that allows you to edit a small set of properties over a large number of

objects. It also allows you to export to and import from CSV files.

PowerDesignerPowerDesigner does not include the Metadata Integration Wizard, choosing instead to rely on several built-in

import engines. If you need additional metadata conversions, you can purchase additional metadata bridges from companies such as Reischmann2. They supply standard bridges, and can configure them quickly for you, if necessary.

The inclusion of the Metadata Integration Wizard means that ERwin appears to have the more capable model import capabilities of the two tools here. In reality though, the majority of data modeling tools can save models in ERwin XML format, which PowerDesigner can import. In fact, it can import and several ERwin files at the same time, and create any combination of conceptual, logical and physical data models from each ERwin file.

The support provided by PowerDesigner for the import and export of model content, such as entity descriptions and comments, is far superior to anything in ERwin. PowerDesigner provides powerful, configurable facilities to export to and import from Microsoft Excel, capable of creating complete models in one pass, including dependencies. No programming is required, though an understanding of the underlying metamodel will help you import some of the more complex metadata, such as dependencies.

Once defined, an Excel import can be re-run whenever you need to — the import definition is an object in its own right, accessible via the browser.

SummaryUsing the OEM Metadata Integration Wizard, ERwin can transfer metadata to and from more tools and formats

than PowerDesigner. Realistically, this apparent advantage is not as great as it seems: the take-on of models in different formats is often a one-off exercise, which can be facilitated by generating ERwin models from your existing tool, and importing them into PowerDesigner. Longer-term import and export requirements can be managed by the excellent bridges supplied by Reischmann.

The ERwin bulk editor allows you to do simple CSV-based import and export; this just cannot be compared to the flexibility of PowerDesigner’s Excel export capability, available from any list of objects or sub-objects, or dependency matrix. Nor is it comparable to the Excel Import Wizard available within PowerDesigner.

1See www.metaintegration.net/ for details of supported formats2See www.reischmann.com/ to find out more

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Other Integration Features

INTERFACES & INTEgRATION FEATuRE POWERDESIgNER 16.0 ERWIN R8.1

Design-time change management Yes Yes

Dedicated data movement/ ETL Model

Yes No

Document data movements Via the Mapping Editor or the Data Movement Model (DMM). A DMM can convert PDM-PDM mappings into a model

Partial

generate scripts to manage the movement of data through the archiving cycle, or data movements

Yes No

generate test data Yes No

build cross-references or traceability links between data model objects and business requirement models

Yes No

build cross-references or traceability links between data model objects and shared business rules

Yes No

Mapping Tool (connections between objects in different models)

Yes No

Persistent Impact Analysis Model Yes No

Export data models in a format that can be imported into other tools

Partial Yes — via Meta Wizard

Import existing data models created by other tools

Partial Yes — via Meta Wizard. Cannot import PowerDesigner LDM. May need to switch off consistency check to import from ER/Studio v9.

Preview, print, and save model comparison results

Yes Yes

Usability

Property EditorsBoth tools provide tabbed editors for editing object properties. As we’ve already seen, ERwin divides an object’s

properties across several different sheets, whereas PowerDesigner supports all properties on a single sheet. Furthermore, the PowerDesigner property sheets can be tailored.

One useful feature of the ERwin property sheet is the ability to choose another object of the same type to edit without closing the sheet. That’s necessary though, as you can’t edit more than one object at a time in ERwin. In PowerDesigner, you have as many object property sheets open as you can handle.

I find the PowerDesigner editors to be clearer than those in ERwin. For example, contrast the PowerDesigner entity and attribute editors shown in Figure 21, with the equivalent from ERwin in Figure 22.

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figure 21. PowerDesigner entity and attribute editors

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figure 22. ERwin attribute editor

Using the model extensions facility (see “Extensibility and Customization” on page 35), we can change the way in which properties are presented in PowerDesigner; you could completely replace the standard tabs with your own.

SummaryThe property editors in PowerDesigner are simpler and more flexible than those in ERwin, and you can open more

than one at a time. If you don’t like them, you can change them. Only PowerDesigner allows you to change the way in which properties are presented in the editors; you could completely replace the standard tabs with your own. See “Extensibility and Customization” on page 35.

Grid-based EditingGrid-based editing allows you to view and edit more than one object at a time, with each object occupying a row in

the grid.

PowerDesignerPowerDesigner provides a grid-like editing mechanism, within the properties of a single object, such as the list

of attributes shown in Figure 21, and also within a list of objects or a List Report. You can customize the properties displayed in the grid, and filter the objects or sub-objects listed. For example, Figure 23 shows a list of relationships that has been customized to show information about the two entities that participate in the relationship. This grid can be used to edit or create relationships, and the content can be exported to Excel. Once outside PowerDesigner, the spreadsheet can be edited in Excel, and the results can be re-imported into PowerDesigner to update the model.

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figure 23. List of relationships in PowerDesigner

The same capabilities are available when editing the attributes of an entity, or even all the attributes in the model. In addition, PowerDesigner allows you to create permanent lists of objects, known as list reports. List reports are stored in the model, and are always accessible from the browser. You can create many list reports for a type of object, and can even save snapshots of the content. Using the snapshots, you can view the properties that used to have in the past. You can open multiple concurrent object lists and object property sheets.

PowerDesigner object lists and list reports provide simple validation capabilities. For example, you can create a list report that contains attributes, and only displays attributes that do not have a domain specified.

ERwinERwin provides a simple grid-based editor, called the “Bulk Editor”, which opens in a separate window. The bulk

editor only allows you to open one grid at a time. Each time you open the bulk editor, you need to run the bulk editor wizard to choose the objects and properties to edit; to make life easier, you can save settings in external files.

SummaryERwin’s Bulk Editor is a pale imitation of PowerDesigner’s grid-based editing capabilities. You can only edit one set

of objects at a time, whereas PowerDesigner allows you to open as many concurrent grids as you can handle; it also remembers your customizations, so you don’t have to save in a file and load them each time.

Diagram StyleData model diagrams are designed to communicate information to an audience. For one audience, you may want to

highlight the entities relating to a given business area. For another audience, you may need to highlight entities that have changed recently. Don’t underestimate the part that diagram style can play in successful communication. We’re not playing with content and color just because it’s fun.

ERwinERwin allows you to create and apply themes, covering default colors, line options and fonts for different object

types. It’s a simple operation to apply a theme to a model, submodel or diagram, and to vary those style components for individual symbols. You can also determine the content of symbols on a submodel, and also for individual symbols, using pre-defined sets of options, which can be tailored for individual diagrams. Figure 24 shows two tables with different colors and content.

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figure 24. Themes in ERwin

Applying a theme to one or more objects is really simple, using previews of the available themes to help you make your choice. The theme is applied immediately.

PowerDesignerIn PowerDesigner, you have more control over the style and content of symbols. Defaults can be set, and shared

via user profiles. As in ERwin, each diagram has default styles and profiles, inherited from a user profile or another diagram. Unlike ERwin, you can’t pick from a list of available themes and have them applied immediately. However, you can ‘get’ the style of one symbol and apply it to other symbols, even symbols of a different type.

The real difference in PowerDesigner is that format and content can be varied from the defaults for each symbol, and the font can be varied for each sub-object. The layout of properties in symbols is also more flexible; the symbols can be laid out with horizontal and vertical property groups, rather than just a single vertical list of properties. You can also specify icons to display on object symbols in place of extended attribute values by creating an attribute icon set with an icon for each possible value. If you want to hide a sub-object on a symbol (such as a hiding an attribute on an entity symbol), you can.

Figure 25 shows a sample PowerDesigner diagram. Every entity is showing three new properties, Plural name, Steward and Review Status. The value of Review Status is shown by the icon at the top of each entity symbol. The style and content symbol for the Contact entity has been customized: fewer properties are shown for attributes, the entity line and fill have been altered, and the font for one of the attributes (Web Address) has been altered to accentuate it.

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figure 25. Colors, fonts and style in PowerDesigner

SummaryThe Themes in ERwin make it easy to apply a custom style to symbols. Unfortunately, the style options end there.

You can adjust the content of symbols, but only by model or sub-model. PowerDesigner does lack the ease of use of ERwin’s themes; instead you can apply a user profile that changes the default symbol style. You can apply it to existing objects if you want to, though it’s not as straightforward to do.

Where PowerDesigner really beats ERwin is the control you have over exactly which sub-objects are displayed on a symbol, and the style and content of individual symbols.

Extensibility and CustomizationWorking with a data modeling tool will require some adjustment of the modeler to the tool and some tool

modifications for the enterprise and the modeler. Extensibility and customization needs will vary with the type of work being done as well as the needs of the organization. This section is concerned with the ability of the tool to adjust to the needs of the environment.

Greater extensibility in a tool is not going to be a concern if simple databases are going to be created and the maintenance will be minimal. Both tools provide adequate features for this activity, though some users may find problems with incomplete DBMS support in ERwin.

To create a model-driven environment, however, more customization is needed. Extensibility exists in a variety of perspectives. Support for DBMSes can be added or their definition files can be modified. The user interface can be adjusted or user profiles can be created. Model creation can be based on a template and naming standards can be employed. User securities can be invoked, at the model or repository level. Reports can be defaulted or customized. Adding scripts is another method of extending the functionality of the data modeling tool. Modifying model checking criteria is useful as well. Perhaps one of the more important levels of extension or customization is the ability to extend model definitions through the use of metaclass, stereotype and object creation.

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PowerDesignerPowerDesigner has vast customization capabilities. To start, look at the architecture of PowerDesigner. It has a

core program file that reads “resource files” in order to perform various functions and support different databases. PowerDesigner uses these files to define the objects for each model and the methods for generating and reverse-engineering them. The resource files are XML files that can be viewed, edited, copied by experienced users. Specifically for databases, there is a resource file, or XML file, for each database supported. There is a file for Oracle 11g as well as a file for Oracle 10gR2. PowerDesigner supplies a comprehensive resource editor that is accessible through the user interface.

PowerDesigner takes the extension and customization concept considerably further than its competitors. At any point in the modeling process, regardless of the type of model, metaclasses can be added. (A metaclass is a special kind of class that has, as its instances, classes. A class would normally have an object when instantiated. This is a concept that has its origins in object-oriented programming but extends to modeling. The instantiation of a metaclass is a class, which, when instantiated, would produce an object.) A PowerDesigner modeler or administrator can create a metaclass, which would serve as the parent of a set of classes/objects to be created later. This can enforce standards and adherence to the organization’s modeling rules. The benefit is that all classes from that metaclass would have the same characteristics and can enforce standardization throughout the organization.

Essentially, PowerDesigner allows any modeler to create new objects or properties of objects to include in their models. Once created, these objects and properties are treated in exactly the same way as any other object in PowerDesigner. They can be included in reports and dependency matrices; new objects have their own property sheets, which the user is in control of; they can be imported from or exported to Excel; they can replace existing properties; if the same objects and properties are defined for two related types of model, they are automatically transferred during model generation.

Stereotypes, in modeling, are created from classes or metaclasses. Stereotypes are typically used for an instance of a class or object. They are typically used for sub-classification purposes. PowerDesigner supports full stereotyping.

PowerDesigner permits user profiles to be created. These profiles standardize the look-and-feel of the modeling environment. Display preferences, model options, check model and other PowerDesigner attributes can be stored and deployed to users as needed. In addition, role-based profiles can be created, allowing the user interface to vary between different types of user.

ERwinERwin has customization for toolbars and the general modeling environment. Beyond that, though, the tool falls

short in terms of extensibility and customization, limited to simple user-defined properties, which cannot be shown on diagram symbols. ERwin is reasonably effective as a “vanilla” modeling tool, but should not be considered for complex environments that require adapting the tool to the environment.

SummaryCustomization and extensibility is one of the key strengths of PowerDesigner. ERwin forces you to work in a

particular way; it is focused on a few key tasks. PowerDesigner, on the other hand, allows you to work in a way that suits you. If you want to manage new objects, properties or object links, you can. If you want different groups of users to experience PowerDesigner in different ways, you can.

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Other Usability Features

uSAbILITy FEATuRE POWERDESIgNER 16.0 ERWIN R8.1

Projects to hold related models and other files, managed as a simple entity in a repository

Yes No

Contextual help Yes Some — Help file opens in Internet Explorer

Excel import and export of object properties

Built-in Limited facility in Bulk Editor

Explorer browser object navigation Yes Yes

Find objects in current model — search names

Yes Yes — one hit at a time

Find objects in current model — search other properties

Yes Can search all properties, but cannot specify which ones

Find objects in selected models — search names

Yes Yes

Find objects in selected models — search other properties

Yes Yes — via SQL queries in the query tool.

Find/replace text in names No * Finds one property at a time — couldn’t find ‘date’ in an attribute name, even though it was present in at least two names* cannot specify object type or property to search* confusing to use — search ‘backward’ and ‘forward’ in model — a model is not a serial thing!

global find/replace text in a single property

Via RTF editing (e.g. in MS Word)

Yes

global find/replace text in other properties

No * Finds one object/property at a time* cannot specify object type or property to search

Lasso multiple objects and access right mouse options

Yes Limited to deleting or grouping symbols, and overriding fonts and colors

N-level undo/redo Yes Yes

Object placement controlled by user Yes Yes

Sample models supplied Yes Only 1 sample model (eMovies.erwin) is small enough to open in evaluation version

Spell check — for a property Yes within text editor — one property

Spell check — global Yes No

Spreadsheet-like editing Yes Limited bulk editor

Tabbed property editor interface Yes Yes

Annotate diagrams with additional symbols to improve communication

Yes Yes

Auto layout diagrams Yes Yes

Auto-include new objects on current diagram (when created via browser)

Yes Yes

Diagram overview window No Yes

Diagram zoom in/out Yes Yes

Diagram zoom window No No

Edit properties within diagram symbols Any non-calculated non-collection property

Only names

Marquee lasso zoom Yes No

Page grid Yes Yes

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uSAbILITy FEATuRE POWERDESIgNER 16.0 ERWIN R8.1

Save Diagram Image in graphics file Selected parts of a diagram — several formats available

One or more complete diagrams

Configure user interface according to user profile

Yes No

Customizable display preferences of any attribute/user-defined attribute

Yes No

Customizable property sheets Yes No

Customize Toolbars and Menus Full customization capabilities for toolbars and menus; can be made dependent on the profile of the user

Yes

Expandable Property Editors Yes No

Automation of common modeling tasks

(such as merging or splitting an entity, or resolving a many-to-many relationship)

Yes Yes

Multiple Model diagrams visible at same time

Yes Yes

Templates for Model Creation Yes Yes

Wizard-driven Task Completion Yes Yes

Workspaces to hold working sets of models and projects

Yes No

Edit multiple concurrent property sheets Yes — can edit properties for numerous objects concurrently

No

Auto-routing of link symbols Yes psgr automatically re-routed as symbols on the diagram are drawn, deleted or moved.

No

bridging of overlapping link symbols Yes No

Moving a relationship end to a different entity without deleting and re-creating the relationship

Yes No

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Adding vAlue to dAtA modeling

Managing Models as a ProjectPowerDesigner provides the concept of a project. A Project is a container to hold related models and other files,

managed as a simple entity in a repository, as a single folder in a local workspace, and as a file folder in your Windows file system. Projects are treated as container objects by the repository; they can be checked in and out, versioned and compared, the same as an individual model.

Projects provide a special kind of diagram, where the symbols represent models in the project, or related models or external files, either within or outside the project. Figure 25 shows a typical project diagram, in this case showing the models created during this tool review, including the ERwin and ER/Studio models that contain a CDM imported from PowerDesigner. I drew the dashed lines to the ERwin and ER/Studio models, all the other lines were drawn by PowerDesigner, reflecting the dependencies stored in the models. The display preferences for the diagram were amended to show a particular property on each dependency, to make the purpose of each one clear.

figure 26. Sample project diagram

Every single model on this diagram (including the ER/Studio and ERwin models) is held under version control in the PowerDesigner repository. Double-clicking any model icon will cause the model to be opened, in ER/Studio or ERwin if necessary.

Figure 27 shows the same project, as viewed in the Browser. On the local workstation, all the files, except those with a shortcut icon in the symbol (the ER/Studio and ERwin models) are stored in the project ‘directory’, a nominated Windows folder. The folder structure shown here is replicated in the repository.

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figure 27. Project in PowerDesigner browser

ERwin does not support anything equivalent to the PowerDesigner Project.

Dependency MatricesAs we saw above, it is important to be able to trace the dependencies for a given object. We can refer to this

as vertically tracing dependencies. It is equally important to be able to trace dependencies horizontally, to take a particular type of dependency between two models, and to examine the objects that take part in it. Indeed, the horizontal dependencies within a model are also important. For example, we may want to see the dependencies between entities or attributes in a SAM, and the entities or attributes in the LDM that was generated from the SAM. We may also want to see the dependencies between domains and attributes within a LDM.

You can access this kind of information within ERwin using reports and macros, but the tool doesn’t provide a standard mechanism for viewing and editing these dependencies.

PowerDesigner does provide such a mechanism, the Dependency Matrix. This allows you to represent any model dependencies in a matrix. Usually, the dependency you’re interested in will be direct, such as the link between LDM domains and attributes, illustrated in Figure 28.

figure 28. Domain/attribute matrix

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Matrices can also depict indirect dependencies, such as the link from data items to entities in a CDM. In a PowerDesigner CDM, data items are instantiated as attributes in entities, so the relationship between data items and entities is not direct. To create a matrix cross-referencing data items with entities, you must trace the links through the metamodel using a dependency path definition, shown in Figure 29. The path starts with the data item, follows the ‘attributes’ property to discover all linked attributes, then follows the ‘entity’ property for each attribute to discover the name of the entity. The resulting matrix is also shown in Figure 29, with entities in the columns, and data items in the rows.

figure 29. Indirect path definition

ERwin does not support anything equivalent to the PowerDesigner Dependency Matrix.

www.sybase.com

Sybase, Inc. Worldwide HeadquartersOne Sybase DriveDublin, CA 94568-7902U.S.A1 800 8 sybase

Copyright © 2012 Sybase, Inc. All rights reserved. Unpublished rights reserved under U.S. copyright laws. Sybase, the Sybase logo, Avaki, DataArchitect, PowerDesigner, Replication Server and SQL Anywhere are trademarks of Sybase, Inc. or its subsidiaries. ® indicates registration in the United States of America. SAP, the SAP logo and SAP NetWeaver are the trademarks or registered trademarks of SAP AG in Germany and in several other countries. All other trademarks are the property of their respective owners. L03122 1/12

ConClusionsCreating a database is a simple task. Creating a database so that it properly supports business requirements makes

it a more difficult task. Developers need to build applications that utilize the databases and database designers must create the databases efficiently. Modelers need to be able to communicate effectively with business stakeholders and developers throughout database and application development processes.

Data modeling is more than just designing and creating databases, though. We need to build subject area models and logical data models to communicate with other areas of the organization, and to integrate with the models that they produce. Most data modeling tools can’t compete in that world.

Choosing a data modeling tool is not a trivial task, even though it appears to be. Both of the tools reviewed in this white paper are competent enough at the bread-and-butter modeling of databases for the majority of organizations. Both will create a logical data model and physical data model, propagate changes from one to another and create database scripts. Both will reverse engineer databases. But they are not at all equal.

Based on my evaluation of these products, PowerDesigner is head and shoulders above the rest. As a modeling and metadata management professional, I would highly recommend PowerDesigner. Not only does PowerDesigner support all the facets necessary for basic database design and development, but it goes “above and beyond” in delivering the functionality to support a model-driven architecture. PowerDesigner allows conceptual data modeling to be performed in the same tool as logical and physical data modeling. Data elements can be tied to business requirements and classes can be created to jump start development through Business Process Modeling and Object Oriented Modeling, respectively. Add in the functionality provided by Model Extensions, User Profiles, Projects, Framework Matrices and Dependency Matrices and the result is a complete modeling tool for the enterprise: PowerDesigner.

ACknowledgementsThe author wishes to thank Sybase and CA for their help in checking the accuracy of his statements about the

products under review. He must also thank the following other organizations for sharing their expertise:IPL Information Processing Ltd, United Kingdom www.ipl.comSandhill Consultants Ltd, United Kingdom www.sandhill.co.ukThe author also wishes to thank Steve Hoberman for permission to use images and models from ‘Data Modeling

Made Simple with PowerDesigner’.

BiBliogrAphyHoberman, S. (2009). Data Modeling Made Simple (2nd ed.). Bradley Beach, New Jersey: Technics Publications, LLC.Hoberman, S., & McGeachie, G. (2011). Data Modeling Made Simple with PowerDesigner.

ABout the AuthorGeorge McGeachie has worked in the field of data modeling and metadata for many years, in a variety of industries.

George has used, implemented and tailored various data modeling and metadata management tools in that time, and has always been regarded as a power user for whichever tool is in use, finding new ways of exploiting their capabilities.