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Re: use case definition

From: Andrew Thackrah <andrew@opengroup.org>
Date: Wed, 14 Aug 2002 17:03:50 +0100
To: www-qa-wg@w3.org
Cc: www-qa@w3.org
Message-ID: <20020814170350.A26934@hyperion>

On 2002.08.14 16:29 Lynne Rosenthal wrote:
> I propose the following definition for use case.  I've also included 
> some additional possibilities. It may make sense to use some of this 
> (#2-4) in the Notes below the checkpoint.  #5 is a definition for User 
> Scenario

> However, here is some Background or alternative definition
> 
> 2. A use case defines a goal-oriented set of interactions between 
> external actors and the system (specification) under consideration. 
> (Actors are parties outside the system that interact with the system 
> (UML 1999, pp2.113-22.123)
> An actor may be a class of users, roles users can play or other systems.


> 5.  USER SCENARIO - an instance of a use case, representing a single 
> path through the use case.  Thus, there may be a scenario for the main 
> flow through the use case and another scenarios for each possible 
> variation of flow through the use case (e.g., representing each option).


  In UML (1.4) , they talk of UseCases and UseCaseInstances.

  They define a UseCaseInstance as (pp2-138):

	" A use case instance is the performance of a sequence of actions 
specified in
	the use case.

  	[In the metamodel UseCaseInstance is a subclass of Instance.]
	Each method performed by a UseCaseInstance is performed as an 
atomic
	transaction; that is, it is not iterrupted by any other 
UseCaseInstance.

  	An explicitly described UseCaseInstance is called a scenario"

  So the OMG regard a scenario as being a description of an instance of a 
use case.
  This is the opposite sense to our current definition in specGL #1.
  "A Use Case is a description of the user scenario"

  So I think we have to decide whether to go with OMG terminology or use 
our own.
  I vote for going with OMG.

  -Andrew
Received on Wednesday, 14 August 2002 12:04:52 GMT

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