What is the difference between use case model and use case diagram?

Answer 1

Use Case diagrams are behavior diagrams of UML used to describe a set of actions (Use Cases) that some system or systems (Subject) should or can perform in collaboration with one or more external users of the system (Actors).

Each use case should provide some observable and valuable result to the actors or other stakeholders of the system.

Use case diagrams are a means for specifying:

• (external) requirements on a system under design, required usages of a system - to capture what a system is supposed to do;
• the functionality offered by existing system -- what system can do for clients;
• requirements the specified system poses on its environment - by defining how environment should interact with the system so that it will be able to perform its services.

Answer 2

Use Case diagrams are behavior diagrams of UML used to describe a set of actions (Use Cases) that some system or systems (Subject) should or can perform in collaboration with one or more external users of the system (Actors).

Each Use Case describes a unit of complete and useful functionality, some observable and valuable result that the subject provides to its users (actors)or other stakeholders of the system.

Example use cases for bank ATM are: Withdraw Cash, Make Deposit.

Use case diagram for ATM could show users of ATM, some or all of use cases, boundary of the system. See example in provided link.

Answer 3

See examples of FAQs related to use case diagrams in the provided link.

Answer 4

A use case model is an abstract idea. A use case diagram is a concrete type of use case model.

Answer 5

Use case diagrams can be drawn using CASE tools. Use case diagrams have following basic components actors, use case, relationship between them.