Generally,
This last quote is very important in regard to the process to be described in the following chapters, and also sets the stage for the possibility of automation through transformations as in Rational Software Architect and Rational Software Modeler (RSx).
Artifact
An artifact is defined as any item that describes the system, including a diagram, matrix, text document, or the like.
Use case
A use case is a sequence of events that describes the collaboration between the system and external actors to accomplish the goals of the system. In other words, the use case is a way to specify the behavior required of the system and external entities in response to a given sequence of stimuli.
This definition is different from the standard definition of use case as found in virtually all the literature on use cases. The authors of the Systems Journal article explain:
In working with the systems community, who typically interact with large teams requiring precise communications, we found that the common informal definition of a use case (namely, a description of a service that the software
provides, which provides value to the actor) is inadequate for a variety of reasons. A service … is a behavior of the system. The actual semantics of
use cases more closely resemble collaboration than behavior. Value is far too subjective a term to be included in the definition of a framework element. In any case, the entity receiving benefit from the system behavior might not include the actors in the collaboration. In addition, the software definition of a use case does not provide for scalability.
This definition provides scalability because it is isomorphic with the definition of an operation, that is, they both consist of a sequence of events. In fact, the difference is one of context, as will be seen below. Operations at any given level
are instances of one or more use cases for entities at the next lower level. Also note that this does not emphasize a sequence of steps, but rather emphasizes the
collaboration.
Chapter 2. Definitions, design points, and key concepts | 19 |