UML/RUP Case study MapQuest
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Requirements Gathering
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Use cases are used in requirement gathering.  Once a task is identified it is called use case. 
Use case is made of sequence of activities.  Portion of use case instance is called flow.  
Use case can be made of three flows:
Main, Alternate, Exceptional are all part of this use case
Optional: is what becomes extend relationship is separate use case
Common/Factored: becomes include relationship is separate use case

Here we want to build system mapquest which lets user get directions to destination address 
from starting address.

Use Case: 
Name: Compute Address
Description: same as above
Main Flow:
  -system prompts user for from/to address
  -user enters from/to address
  -user submits
  -system computes 
  -system displays shortest path
  -system displays links to faster and another path
  -user leaves
Alternate Flow: None
Exception Flow: Invalid address

An activity diagram (fancy flow chart) can be used for above activities.

Scenario1: user chooses main flow
Scenario2: user chooses main and then shortest path
Scenario3: user choose main and then another path
Scenario4: invalid address

Extension points: faster path, another path


If we had option to choose between shortest, fastest, another then they would be all alternate 
flows and one selected as main flow.  Our modifications to use case and scenarios would be 
then as below.

Main Flow: shortest
..
..
Alternate: fastest, another
Extenstion: None
Exception: Invalid Address

Scenario1: user chooses main flow
Scenario2: user chooses shortest path
Scenario3: user choose  another path
Scenario4: invalid address


Use case Model has use case diagrams.
use case diagram has Actor, use case (system), communication (association)
use case has relationships: include (common), extend (optional), generalize (specialize)

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From here we use CRC to get entities.  

Design will involve doing framework (architecture), design patterns, detailed design 
(signatures).

If in future our requirements changes that user should be made to select shortest/fastest 
then we could make both as extend since now base will include only get address as include.

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