Explain “Use Case” diagram. What are the essential criteria for ideal use case diagram? What are the “extends” and “includes” constructs in use case diagram? Draw a use case diagram for Nursing Home functionality where examples of actors are Patient, Doctor, Reception Staff, Billing Staff and Administrator etc.
Use Case Diagram:
A use case diagram is a representation of a user's interaction with the system that shows the relationship between the user and the different use cases in which the user is involved. The purpose of use case diagram is to capture the dynamic aspect of a system. But this definition is too generic to describe the purpose.
Essential criteria for ideal use case diagram:
1) The name of a use case is very important. So the name should be chosen in such a way so that it can identify the functionalities performed.
2)Give a suitable name for actors(actors can be human user, some internal applications or may be some external applications)
3)Show relationships and dependencies among the use cases and actors clearly in the diagram.
“extends” constructs in use case diagram:
Extends constructs means that One Use Case can extend the behavior of another, typically when exceptional circumstances are encountered. For example, if a user must get approval from some higher authority before modifying a particular type of customer order, then the <get approval> Use Case could optionally extend the regular <modify order> Use Case.
“includes” constructs in use case diagram:
Includes constructs means that one Use Case could include the functionality of another as part of its normal processing. Generally, it is assumed that the included Use Case is called every time the basic path is run. For example, when listing a set of customer orders to choose from before modifying a selected order, the <list orders> Use Case would be included every time the <modify order> Use Case is run.
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