Software Development PracticesICT 0801
1
S.G.Nambuwasam
7/29/2011
What is Softwarey Software is a general term for the various kinds of programs
used to operate computers and related devices. y Software can be thought of as the variable part of a computer and hardware the invariable part.
Software Developmenty Is the act of working to produce/create software. This
software could be produced for a variety of purposes.
Reasons to Develop Softwarey to meet specific needs of a specific client/business y to meet a perceived need of some set of potential users y for personal use
Software Development Life Cycle (SDLC)y Market research y Gathering requirements for the proposed business solution y Analyzing the problem y Devising a plan or design for the software-based solution y Implementation (coding) of the software y Testing the software y Deployment y Maintenance and bug fixing
Popular Software Development ModelsA. System Development Life Cycle (SDLC) Model B. Prototyping Model C. Rapid Application Development Model D. Component Assembly Model
System Development Life Cycle (SDLC)y The systems development life cycle (SDLC) is a sequential
conceptual model used in project management that describes the stages involved in an information system development project, from an initial feasibility study through maintenance of the completed application.
Activities of SDLC 1. System/Information Engineering and Modeling 2. Software Requirement Analysis 3. System Analysis and Design 4. Code Generation 5. Testing 6. Maintenance
Stages of the Waterfall Model
Requirement Analysis & Definitiony The requirements are gathered from the end-user by
consultation y Requirements are analyzed for their validity and the possibility of incorporating the requirements in the system to be development is also studied y A Requirement Specification document is created which serves the purpose of guideline for the next phase of the model
Feasibility Studyy Aims to objectively and rationally uncover the strengths and
weaknesses of the existing business or proposed venture, opportunities and threats as presented by the environment, the resources required to carry through, and ultimately the prospects for success y Criteria to judge feasibilityy Cost required y Value to be attained
Five Common Feasibility Factorsy Technology and System Feasibility y Economic Feasibility y Legal Feasibility y Operational Feasibility y Schedule Feasibility
Other Feasibility Factorsy Market and real estate feasibility y Resource feasibility y Cultural feasibility y Financial feasibility
Feasibility Study Reporty The feasibility study outputs the feasibility study report y A report detailing the evaluation criteria, the study findings,
and the recommendations
System & Software Designy The requirement specifications from first phase are studied in
this phase and system design is prepared. y Helps in specifying hardware and system requirements y Helps in defining overall system architecture y Serve as input for the next phase of the model
Implementation & Unit Testingy the work is divided in modules/units and actual coding is
started y The system is first developed in small programs called units, which are integrated in the next phase. y Each unit is developed and tested for its functionality;
Integration & System Testing:y Units are integrated into a complete system during
Integration phase and tested to check if all modules/units coordinate between each other and the system as a whole behaves as per the specifications. y After successfully testing the software, it is delivered to the customer.
Operations & Maintenance:y virtually never ending phase (Very long) y the issues related to the system are solved after deployment
of the system
Waterfall development in actioncreate the functional specification 2. When we have a full understanding of the business the functional specification is published and distributed to as many business experts as possible for feedback. 3. When the functional specification is final we often convey a meeting of business experts and work through the final copy together to iron out any errors prior to sign-off.1.
4. 5.
6. 7. 8.
produce a non working prototype application along with a user interface specification When everybody is happy that the screens will deliver the functionality required the application can be developed and tested. When the application is complete a beta release is published and provided to the business for testing. Any bugs found are rapidly repaired When no significant bugs remain and the client is happy with the application it can go live as release version 1.0.
Advantages of the waterfall methody Design errors are captured before any software is written saving y
y y
y
time during the implementation phase. Excellent technical documentation is part of the deliverables and it is easier for new programmers to get up to speed during the maintenance phase. The approach is very structured and it is easier to measure progress by reference to clearly defined milestones. The total cost of the project can be accurately estimated after the requirements have been defined (via the functional and user interface specifications). Testing is easier as it can be done by reference to the scenarios defined in the functional specification.
Disadvantages of the waterfall methody Clients will often find it difficult to state their requirements
at the abstract level of a functional specification and will only fully appreciate what is needed when the application is delivered. It then becomes very difficult (and expensive) to re-engineer the application. y The model does not cater for the possibility of requirements changing during the development cycle. y A project can often take substantially longer to deliver than when developed with an iterative methodology such as the agile development method.
Prototyping Modely The basic idea here is that instead of freezing the
requirements before a design or coding can proceed, a throwaway prototype is built to understand the requirements. y prototype is developed based on the currently known requirements. y By using this prototype, the client can get an "actual feel" of the system, since the interactions with prototype can enable the client to better understand the requirements of the desired system.
y Prototyping is an attractive idea for complicated and large
systems for which there is no manual process or existing system to help determining the requirements. y It is also an effective method to demonstrate the feasibility of a certain approach. y might be needed for novel systems where it is not clear that constraints can be met or that algorithms can be developed to implement the requirements.
Prototyping Model
Stages of the Prototyping Modely cyclic version of the linear model y once the requirement analysis is done and the design for a
prototype is made y the development process gets started y Once the prototype is created, it is given to the customer for evaluation y The customer tests the package and gives his/her feed back to the developer who refines the product according to the customer's exact expectation
y After a finite number of iterations, the final software package
is given to the customer. y In this methodology, the software is evolved as a result of periodic shuttling of information between the customer and developer. y the most popular development model in the contemporary IT industry. y Most of the successful software products have been developed using this model
Advantages of Prototypingy Users are actively involved in the development y It provides a better system to users, as users have natural
tendency to change their mind in specifying requirements and this method of developing systems supports this user tendency. y Since in this methodology a working model of the system is provided, the users get a better understanding of the system being developed. y Errors can be detected much earlier as the system is mode side by side.
y Quicker user feedback is available leading to better solutions. y One of the key advantages a prototype modeled software has
is the time frame of development. Instead of concentrating on documentation, more effort is placed in creating the actual software. This way, the actual software could be released in advance.
Disadvantages of the Prototyping Modely Leads to implementing and then repairing way of building
systems. y Since its being built out of concept, most of the models presented in the early stage are not complete. y Practically, this methodology may increase the complexity of the system as scope of the system may expand beyond original plans. y integration could be very difficult for a prototype model.
Rapid Application Development Modely A linear sequential software development process y An extremely short development cycle y The RAD model is a "high speed" adaptation of the linear
sequential model y Rapid development is achieved by using a component-based construction approach. y Used primarily for information systems applications,
Phases of RAD1. 2. 3. 4. 5.
Business Modeling Data Modeling Process Modeling Application Generation Testing and Turnover
Business Modeling The information flow among business functions is modeled in
a way that answers the following questions: What information drives the business process? What information is generated? Who generates it? Where does the information go? Who processes it?
Data Modelingy The information flow defined as part of the business
modeling phase is refined into a set of data objects y The characteristic (called attributes) of each object is identified and the relationships between these objects are defined.
Process Modelingy The data objects defined in the data-modeling phase are
transformed to achieve the information flow necessary to implement a business function. y Processing the descriptions are created for adding, modifying, deleting, or retrieving a data object.
Application Generationy Works to reuse existing program components (when
possible) or create reusable components (when necessary). y In all cases, automated tools are used to facilitate construction of the software.
Testing and Turnovery The RAD process emphasizes reuse, many of the program
components have already been tested. y This minimizes the testing and development time.
Advantages of RAD1. Flexible and adaptable to changes. 2. Prototyping applications gives users a tangible
description from which to judge whether critical system requirements are being met by the system. Report output can be compared with existing reports. Data entry forms can be reviewed for completeness of all fields, navigation, data access (drop down lists,checkboxes, radio buttons, etc.). 3. RAD generally incorporates short development cycles - users see the RAD product quickly.
RAD involves user participation thereby increasing chances of early user community acceptance. 5. RAD realizes an overall reduction in project risk. 6. Reduce the cost to create custom system.4.
Disadvantages of RADUnknown cost of product. As mentioned above, this problem can be alleviated by the customer agreeing to a limited amount of rework in the RAD process. 2. It may be difficult for many important users to commit the time required for success of the RAD process.1.
Component Assembly Modely leads to software reusability y The integration/assembly of the already existing software
components accelerate the development process. y is an iterative development model y It works like the Prototype model, constantly creating a prototype until a software that will cater the need of businesses and consumers is realized. y has a close resemblance with the Rapid Application Development (RAD) model.
7 uses the available tools and GUIs to build software. 8 If the right components are chosen, the integration aspect is made much simpler.
