IMS 5024

IMS 5024, Semester 2, 2002 Lecture 5

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IMS 5024

Event-driven modelling


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Content

• Individual assignment• Pitfall revisited• Group assignment• BSD• SAP R/3• Place in ISD• Evaluation of event driven modelling• Reading list for next week


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Individual assignment

Date due: 29 August 2002 – Difference between social and

technical–Show understanding of the

subject matter–Questions e-mail Bahar directly


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Teaching Assistant

• Bahar Jamshidi

• E-mail: [email protected]

• Queries about marks• Other queries• Thursday 6 – 7 PM

mailto:[email protected]









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My consultation times

• Monday 10 – 11.30 am

• Tuesday 2 – 3.30 pm


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Pitfalls

• Not starting early

• Reading, more reading and then some reading.

• Plagiarism !!!!!


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Different perspectives

• Process

• Data

• Behaviour / Stimulus response – how system reacts to external and internal events

• Difference


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Techniques

• State transition diagrams

• Business rules diagram (BRD)

• Event-driven process chain methodology

• Petri nets

• Finite state machines


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Key constructs of BRD

State Event Condition

Signal Blob


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Definition of a business rule

• An explicit state change context in an organisation which describes the states, conditions and signals associated with events that either change the state of a human activity system so that subsequently it will respond differently to external stimuli or reinforce the constraints which govern a human activity system


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Business rule types

Implementation rules

Processing rules

Policy rules


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Steps in creating BRD

• Identify candidate business (policy) rules• Identify candidate events and signals• Identify candidate objects in problem situation• Construct object life histories (OLH) for each

object identified• Construct user business rule diagrams (UBRD)• Construct business rules diagram• Construct event specification table (EST)


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Example of candidate business rules (Policy rules) (1)

• Orders sent by mail or telephone• Omissions on order line leads to deletion• Credit balance >= order value to accept order else

reject• Stock qty >= order qty to accept order otherwise

reject• One invoice for one order• Sum of payments = order value – sum of credit notes• One order may have many credit notes


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Example of candidate business rules (Policy rules) (2)

• Many payments per invoice possible• Overdue invoices occur 30 days after statement• If product not carried reject item• If unobtainable multiples reject item• New order created for outstanding items• Only good customers may obtain credit orders• Credit balance reduced for all items on an order

including outstanding items


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Example of candidate list of business events and signals

Receive customer order TDelete line EReject order ECreate new order ESend invoice MGenerate credit note EReceive payment TCreate outstanding item ECreate new customer EMove to good customer EMove to bad customer E


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Example of a OLH

Customer Tempcust

Goodcust

Badcust


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Example of UBRD


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Example of BRD


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Example of EST


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SAP R/3

• Why?Blend business processes and technology

• Best practice processes – then focus on unique aspects

• Blueprint used as reference model

• Business process takes center stage


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Blueprint

• Help organisations to define needs, develop solutions and optimize their processes

• Do not need to start from scratch• Customisation possible• Include functions, process, information

flow and organisation views• Business processes are shown in the Event-

driven process chains


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Modelling approach

• Define / redefine the organisations goals

• Create a model to reflect the goals

• Develop unique applications

• Implement the applications


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SAP approach

• Map company processes to the blue print (reflect “best practice”)

• Define target situation

• Focus on unique aspects

• Customize and configure


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Key elements of SAP blueprint

• Events (when should something be done?)

• Tasks or functions (what should be done?)

• Organisation (who should do what?)

• Communication (What information is required to the right task?)


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Event-driven process chain (EPC) methodology (1)

• Event e.g.. Goods arrived

• Task / function e.g.. Verify goods

• Organisation e.g. Good receiving dept

• Information e.g. Delivery note


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Event-driven process chain (EPC) methodology (2)

• Process path

• Logical operator

• Control flow

• Information/material flow

• Resource/organisation unit assignment

Xor


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Legend

• EPC is the central view

• Event always trigger a task

• Start and end with an event

• Organisational units are added

• Navigation between process models by start and final event


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Example of an EPC


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Other views

• Component model – describe what is done

• Organisation model – Who does what and who is responsible

• Data model – what is needed to do something

• Interaction model – what information must be exchanged between different units


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Example of a component model


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Example of Organisation model


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Example of data model


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Example of an Interaction model


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Evaluation of Data modelling

Problem oriented Product oriented

Concep-tual

Structured analysis

Entity relationship modelling

Logical construction of systems

Modern structured analysis

Object oriented analysis

Structured design

Object oriented design

Formal PSL/PSA

JSD

VDM

Levels of abstraction

Stepwise refinement

Proof of correctness

Data abstraction

JSP

Object oriented programming


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Advantages of Event driven modelling

Concentrate on the problem area Identify business processes Cost


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Disadvantages of event driven modelling

• Difficult to implement

• Early days

• Cost


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Process modelling view of ISD

Development group

Objectives

Environment

Object system

ObjectsystemChange

process

Hirschheim et al see reading list


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Reading for next week

• Rumbaugh, J., Blaha, M., Premerlani, W., Eddy, F., Lorensen, W. (1991) Object oriented modeling and design. Prentice Hall, Inc. USA. Chapter 1,2,3,4

IMS 5024

Documents

order qty

itemnew order

order line

credit notesims

eventdriven modellingims

credit orderscredit

good customeremove

outstanding itemsims