1

Use Cases 2

CSSE 371 Software Requirements and Specification

Mark Ardis, Rose-Hulman InstituteSeptember 20, 2004

2

Outline Computing in 1968 Template for use cases Extending use cases Including use cases

3

Computing in 1968

4

Computing in 1968

5

Computing in 1968

6

Computing in 1968

7

Doug Engelbart Video

(see link from ANGEL course page)

8

Refining Use Cases Describe sequences of events for flows Describe pre-conditions Describe post-conditions Fill in special requirements

9

Use Case Template

A. NameB. Brief descriptionC. ActorsD. Basic flowE. Alternate flowsF. Pre-conditionsG. Post-conditionsH. Special requirements

10

Microwave Example

User

Cook Food

11

Cook Food Use Case 1/4

A. Name: Cook FoodB. Brief description: User places food in

microwave and cooks it for desired period of time at desired power level.

C. Actors: User

12

Cook Food Use Case 2/4

D. Basic flow:1. User opens door and places food in unit2. User enters time for cooking3. User pushes start button4. Unit cooks food5. Unit beeps

13

Cook Food Use Case 3/4

E. Alternate flows1. User cancels time before starting2. User cancels cooking before finished3. User selects reduced power level before

pushing start button

14

Cook Food Use Case 4/4

F. Pre-conditions Unit is plugged in Unit is in ready state

G. Post-conditions Food is cooked or user cancelled operation

H. Special requirements Timer should display remaining time to

finish while cooking Default power setting should be "high"

15

Extending Use Cases

Extend an existing use case instead of redefining it

16

Microwave Extension

User

Cook Food

Slice Food

<<extend>>

17

Including Use Cases

Frequent sequences of events may be defined as use cases

Including a use case is like calling a subroutine

18

Microwave Inclusion

User

Cook Food

Set Timer

<<include>>

19

Cook Food Inclusion

D. Basic flow:1. User opens door and places food in unit2. User performs Set Timer use case3. User pushes start button4. Unit cooks food5. Unit beeps