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Requirements Analysis


The requirements analysis is the first activity in the SOMT method. The purpose of the activity is, as stated above, to capture and analyze the problem domain and the user requirements on the system to be built. For this purpose the system is viewed as a black-box and only the objects and concepts visible on the system boundary and outside the system are modeled.

There are five major models used in this phase:

The textual requirement model is a conventional textual requirements specification. This may come from the customers as input to the development project or it may be created as part of the requirements analysis as a complement to the other models.

The use case model consists of a set of use cases, each described using structured text and/or using MSCs and HMSCs. The purpose of this model is to capture and validate requirements from a user's point of view to make sure that the system will solve the right problem.

The requirements object model is a conventional object model, i.e. one or more diagrams illustrating a number of objects and their relations (including inheritance and aggregation relations). State charts may also be included in the object model to provide high level descriptions of the behavior of important objects. The purpose of the model is two-fold:

The system operation model is a description of the atomic transactions the system must be able to perform. The system operations can be viewed as more detailed specifications of the events that are part of the use cases.

During the requirements phase a data dictionary is also created. The data dictionary is a list of the concepts identified in this phase together with brief explanations of the concepts. It is used and refined throughout all the development phases.


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