Define Use Case and Actor in Use Case Diagram. For the case study given below identify all the actors, use cases and relationship. Also, draw use case diagram.

XYZ Hotel Information System.

 There are two types of customer: Tour-group customers and Individual customers. Both can book, cancel, check-in and check-out of a room by phone or via the Internet. There are booking process clerk and reception staff who manages it. A customer can pay his bill by Credit card or pay utility bill.

customer <<extend>>

A generalization relationship to pay bill

 Use Cases

Use Case Diagram

- Use case diagram is a representation of a user's interaction with the system that shows relationship between the user and the different use cases in which the user is involved.
- It helps to identify, clarify and organize the system requirements.
- It describes the behavior of the target system from an external point of view.
- A use case diagram consists of following components:
1. Boundary
2. Actor
3. Use case
4. Relationship

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Actor

- Actors are the entities that interface with the system.
- Actors are external to the system.
- They may be people, external hardware or other subjects.
- External actors may be primary, supporting and offstage actor.
- Primary actor has user goals fulfilled through services of system under development.
- Supporting actor provides service to system under development.
- Offstage actor has an interest in the behavior of use case.

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Use Case

- It is a specification of a set of actions performed by a system which yields an observable result.
- It represents what the actors want your system to do for them.
- Each use case is a complete course of events in the system from a user perspective.

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Relationships

1. << include >> relationship
- A usecase may contain functionality of another use case.
- It implies that the behavior of the included use case is inserted into the behavior of the including use case.
- It is expressed as a dotted line labelled << include >> beginning at base use case and ending with an arrow pointing to included use case.

2. << extend >> relationship
- Certain use case may be performed as part of another use case.
- It is optional.
- The base use case can complete without the extended use case.
- It changes the behavior of base use case.
- It implies that the behavior of a use case may be extended by the behavior of another use case.

3. Association
- It indicates the communication between an actor and a use case.
- It is represented by a solid line.

4. Generalization
- It is the relationship between general use case and a special use case.


Reference:  http://www.floppybunny.org/robin/web/virtualclassroom/edin_cl1/resources/oot-ch03.pdf