4.43 Elementary Method "Use Case Modeling" (UCM)

  4.43 Elementarmethode "Use-Case-Modellierung" (UCM)

Contents		1 Identification/Definition of the Method 2 Brief Characteristic of the Method 3 Limits of the Methods Application 4 Specification of the Methods Allocation 5 Interfaces 6 Further Literature 7 Functional Tool Requirements Links to the V-Model Mailinglist

1 Identification/Definition of the Method

2 Brief Characteristic of the Method

The objective of this method is to collect and represent functional requirements with regard to a system from the point of view of external actors. The requirements must be described in form of Use Cases. A Use Case can be realized in a set of scenarios. External actors (e. g. staff members, project manager or administrator) represent roles that might be taken over by actual persons, machines, computer tasks or other systems.

A Use Case is initiated by an actor and must be described by means of the dialogues or interactions "required" to handle a task between these actors and the system. The interactions can be specified by a sequence of actions and events started by the initiating actor, the system or other actors. Only such actions or events must be specified that can be recognized from the actors point of view, not, however, details describing how the system has to work internally.

Altogether, the Use Cases specified for a system represent a set of user-oriented functional system requirements. In order to be complete it should be tried to specify all detected Use Cases in this form.

Means of Representation

The method was introduced Ivar Jacobson et al. in the field of object-oriented system development and is part of the complex method "Object-Oriented Software Engineering (OOSE)" /Jacobson, 1992/.

The method is intended for the description of Use Cases in text form. First approaches for a formalized description are discussed by Jacobson in /Jacobson, 1995b/. In addition, the defined Use Cases and their relationships to actors are graphically represented and listed in overview diagrams. Symbols for the representation of the Use Cases, the actors and their relationships are available. It is possible to represent relationships between Use Cases and actors as well as relationships between Use Cases among each other.

Based on the definition introduced by Jacobson, other authors also discuss this method in slightly different versions. Its usefulness for the software development process is recognized by most authors and the path for a shared understanding seems clear /Jacobson, 1995a/. By means of the cooperation of Booch and Rumbaugh with Jacobson, the method has also been integrated into /Booch, 1997/.

Operational Sequence

For practical reasons, the Use Case modeling is realized with the following steps:

• Definition of the logical system limitations (Black Box aspect).
• Detection of the actors (roles) working or communicating with the system.
• Determination of system usage by the relevant actors. Each type of usage is modeled as use case.
• Identification of the initial event or action initiated by a use case.
• Definition of the conditions leading to the completion of a use case.

3 Limits of the Methods Application

4 Specification of the Methods Allocation

5 Interfaces

6 Further Literature

7 Functional Tool Requirements

Links to the V-Model Mailinglist

GDPA Online Last Updated 01.Jan.2002 Updated by Webmaster Last Revised 01.Jan.2002 Revised by Webmaster