1

LECTURE 54/2/16

2

Functional decomposition

T icke t is su ed

P a ym e n t

R e s e rva tion

F lig h t in fo rm a tio n e nq u iry

P a ss en g er

A few words on “assumptions”• Assumptions arise when there is uncertainty about

interpreting observations • There are different ways of interpretation • There are options

• For example, in case of a system dealing with books, should the “author” be an object on its own or an attribute of the book object (i.e. author’s name)? • It depends: for a library system that might suffice, for a publisher

they might need to know a lot about each author having contract with them

A few more words on “assumptions”

• Do not confuse it with • Facts, that may be observed – even if it is the result of analysis • Design decisions – which you make (and record) as you progress

5

More on Activity Diagrams • A good tool for illustrating the logical flow of activities that

take place between the system and the outside world and the outside world or within the system among its components

• Activity diagram has two unique tools i.e. swimlanes and synchronisation bar

6

Activity Diagrams - Swimlanes • This is a vertical partition that organises responsibilities

for actions. • Not limited to objects in a systems• Swimlanes can also represent divisions within an

organisation • E.g.

• Inventory• Shipping• Sales• Accounting

Swimlane Diagrams

Allows the modeler to represent the flow of activities described and at the same time indicate which actor (if there are multiple actors involved in a specific use-case) or class has responsibility for the action described by an activity rectangle

8

Example Activity Diagram

Commuter use a vending machine to buy train tickets. The ticket vending machine will request trip information from

a Commuter. Based on the this information, the machine will calculate payment due and request payment options, these include payment by cash or by debit/credit card. After payment is complete, the ticket is dispensed to the Commuter.

9

10

Summary Activity Diagrams• Popular form of dynamic modelling

• Good at representing the complexities of logical flow

• Swimlanes and synchronisation help to add a level of complexity to the diagram beyond flowcharts and sequence diagrams