A class model is usually created by the business or systems analyst. Working alongside IT, the class model is used to communicate business requirements in a language IT can understand.
A class model is the UML/object-oriented version of a data model. That is, it shows the data to be held within a system and the way the various data items are connected with each other. The concepts involved are similar to those in entity relationship models, but the UML notation has some additional features that enrich our understanding of the data.
A class model shows graphically the classes within a system and their relationships with one and other. In a business system, a class model captures information about the particular things involved in the organisations operations, for example projects, customers and team members for a project control system.
A comprehensive data model is necessary for the following reasons:
Traditionally speaking a class can be anything about which information is to be stored about. In reference to local councils, this could be customers, leisure events, council buildings etc.
A Class is represented by a rectangular container, which contains the name of the class in the top compartment. Attributes are listed in the lower compartment, attributes relate to the things/pieces of data which we need to know about the class.
Classes are linked together by Associations, which will be in the form of a meaningful business phrase linking two classes, for example:
For the effective communication of the class diagram between business and IT, it is critical that the associations are named clearly to reflect the business rules they support.
Numbers at each end of the class association indicate the range of numbers of instances of classes allowed in the relationship.
Possible number ranges could be:
So here with this example of a class association we see that the Customer (class) Submits (relationship) zero or one (multiplicity) Planning Applications (class).
Class models are particularly used at the requirements definition stage of analysis. After completion, with a supporting requirements catalogue, these should be passed to IT to implement the changes. Additionally, other system models such as use cases may be required as well.
For more class model examples and templates, visit http://creately.com/diagram-community/popular/t/use-case
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