Information Technology IMS5024 Information Systems Modelling Event-driven modelling.

Information Technology

IMS5024 Information Systems Modelling

Event-driven modelling

School of Information Management & Systems

8.2

Content

• BRD• SAP R/3• Place in ISD• Reading list for next week


8.3

Different perspectives

• Process• Data• Behaviour / Stimulus response – how

system reacts to external and internal events

• Difference


8.4

Techniques

• State transition diagrams (STD)• Business rules diagram (BRD)• Event-driven process chain (EPC)

methodology• Petri nets• Finite state machines


8.5

Key constructs of BRD

State Event Condition

Signal Blob


8.6

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.”

McDermid 1998


8.7

Business rule types

Implementation rules

Processing rules

Policy rules


8.8

Steps in creating BRD

• Identify candidate business (policy) rules• Identify candidate events and signals• Identify candidate objects in the 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)


8.9

Example candidate business (policy) rules

• Orders sent by mail or telephone• Omissions on order line leads to deletion• Available credit >= order value to accept order

else reject• Available 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


8.10

Further examples

• 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


8.11

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 EChange status to good customer EChange status to bad customer E


8.12

Example object life history

Customer Tempcust

Goodcust

Badcust


8.13

SAP R/3

• Best practice processes – then focus on unique aspects

• Blueprint used as reference model• Business process takes center stage


8.14

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


8.15

Modelling approach

• Define / redefine the organisations goals• Create a model to reflect the goals• Develop unique applications• Implement the applications


8.16

SAP approach

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

• Define target situation• Focus on unique aspects• Customize and configure


8.17

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?)


8.18

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 / resource

e.g. Delivery note


8.19

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

Xor

• Process path

• Logical operator

• Control flow

• Information/material flow

• Resource/organisation unit assignment


8.20

Legend

• EPC is the central view• Event always triggers a task• Start and end with an event• Organisational units are added• Navigation between process models by

start and final event


8.21

Example of an EPC

refer Davis, 2001 fig 9.13


8.22

Elements of EPC

Event set of values for which it has a predefined action if set of values occurs eg credit limit exceeded

IF current document is sales order

AND IF current customer has credit limit

AND IF sales order value > customer credit limit

THEN issue warning to user entering sales order


8.23

Elements of EPC

Functionbrings about a transformation from an initial state to a target state eg verify order, convert currency

• purpose is to do something

• activated by one of a set of events

• operates on information from many sources


8.24

Event Driven Process Chain

Order received

orderentered

Costcalculated

Enterorder

Calculatecost It couldn’t be simpler!

after Fig 7.2 Davis


8.25

Elements of EPC

Organisational Unit• element used in organisational structure - department,

section, person eg sales dept., finance manager• can be defined in terms of material groups processed,

markets served eg steelworks division, juvenile apparel• system organisation units


8.26

Elements of EPC

Information, material or resource object• real world objects• business objects, entities• resource objects eg. energy, services, purchase

order, information system


8.27

X

Elements of EPC

AND - all inputs to symbol must be true for output to occur

XOR (exclusive OR) - one input, but not both, must be true for output to occur

OR (either or both) - either input will suffice on its own, or both may be true to allow output

Logical Operators


8.28

Elements of EPC

Control Flow - time and/or sequence ordering, interdependence of event and function

Information or Material Flow - read, change or write data; movement of material

Resource or Organisational Unit Assignment - unit or staff resource processes or is processed by a function


8.29

Modelling decisions

X

Orderreceived

Checkproduct ordered

Product Arequired

Product Brequired

ManufactureProduct A

ManufactureProduct B


8.30

Rules and Process Flow

• not all processes are strictly sequential flows

• business rules govern processes• rules are tested by conditional branches

• if .TRUE. then do this

• if .FALSE. then do that (or do nothing)


8.31

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


8.32

References

Johnstone & McDermid (1999) “Extending and Validating the Business Rules Diagram Method.” Proceedings of 10th Australasian Conference on Information Systems.

Davis (2001) “Business Process Modelling with ARIS.” Springer-Verlag.


8.33

Reading for next week

Checkland and Scholes (1990) Chapters 1 and 2

Information Technology IMS5024 Information Systems Modelling Event-driven modelling.

Documents

Transcript of Information Technology IMS5024 Information Systems Modelling Event-driven modelling.