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Use case diagrams

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Title: Use case diagrams Created Date: 1/19/2012 1:20:23 PM Document presentation format: On-screen Show (4:3) Company: St. Francis Xavier University – PowerPoint PPT presentation

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Title: Use case diagrams


1
Use case diagrams
  • A use case diagram is UMLs notation for showing
    the relationships among a set of use cases and
    actors
  • A use case diagram can help the software engineer
    to convey a high-level picture of the
    functionality of the system

2
Library system use case diagram
Example Use-case diagram for a course
registration system
3
Create Use Cases Walk Through
  • Identify actors
  • Define use cases
  • Discover reuseable use cases
  • Put uses into tables with id, name, primary
    actors etc.
  • Write use case description for each use case
  • brief description
  • Basic flow
  • Alternative flow

4
Example
5
Identify Reuse In Use Case
6
Create use case index
7
(No Transcript)
8
Use case Description
Use Case Number 1 Use Case Name Buyer Places a
Bid Description An EBAY buyer has identified an
item they wish to buy, so they will place a bid
for an item with the intent of winning the
auction and paying for the item.
9
Basic Flow
Next Describe the happy day scenario for your use
cases such as "placing a bid". For a consumer to
play a successful bid, what is the primary flow
when everything goes as planned. An effective use
cases needs to have the basic flow before moving
forward with writing the alternate flows.
10
Alternative flow
  • A few examples of alternate flows are
  • credit card failed when a customer places an
    order,
  • user session times out when placing an order

11
Extensions
  • Used to make optional interactions explicit or to
    handle exceptional cases
  • By creating separate use case extensions, the
    description of the basic use case remains simple
  • A use case extension must list all the steps from
    the beginning of the use case to the end
  • Including the handling of the unusual situation

12
Generalizations
  • Much like superclasses in a class diagram
  • A generalized use case represents several similar
    use cases
  • One or more specializations provides details of
    the similar use cases

13
Inclusions
  • Allow one to express commonality between several
    different use cases
  • Are included in other use cases
  • Even very different use cases can share sequence
    of actions
  • Enable you to avoid repeating details in multiple
    use cases

14
Example of generalization, extension and inclusion
Example Use-case diagram for a home security
system
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