UML Designer User's Guide


Identifying things and responsibilities

The object model of an OO system usually has a strong correspondence to the actual real-world entities of the domain: for each domain entity (whether physical or intangible), there is generally one or more corresponding implementation objects. This "natural" model helps to make the system understandable, and it also means that changes to the problem domain map well to changes in the software.

To choose the correct objects for the system, you need to identify the required behavior of the objects. With UML Designer, you do this by creating things (domain objects) and assigning responsibilities to them.

In the Adding a new book use case, there are several terms that refer to entities that exist within the system (unlike the librarian, who is outside the system):

These are candidates to become objects in the implemented system. We can now create Thing elements in the Library Catalog model to represent each of these.


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