UML Use Case "extend" and "include" relationships
This use case diagram relationships tutorial will cover all you need to know about relationships in use cases. Learn about include, extend. UML use case include is UML relationship between two use cases to show that Note, while UML 2.x defines extension points for the extend relationship, there. Beware that extend is used in UML quite differently than in e.g. Java. Your diagrams are probably not expressing what you would like them to.
The system determines that the applicant does not already exist within the system according to BR37 Potential Match Criteria for New Students. The system determines that the applicant is on the eligible applicants list. Person is Not Eligible to Enroll] The system adds the applicant to its records.
The applicant is now considered to be a student. The registrar helps the student to enroll in seminars via the use case UC 17 Enroll in Seminar. The student pays the initial fee. The system prints a receipt.
The registrar hands the student the receipt. The use case ends. Include Dependencies Between Use Cases A second way to indicate potential reuse within use-case models exists in the form of include dependencies. An include dependency, formerly known as a uses relationship in UML v1. The best way to think of an include dependency is that it is the invocation of a use case by another one. The blue test in Figure 2 presents an example of how you would indicate where the use case is included in the logic of the including use case.
- UML Use Case "extend" and "include" relationships
- UML Use Case Include
Similar to calling a function or invoking an operation within source code, isn't it? You use include dependencies whenever one use case needs the behavior of another. Introducing a new use case that encapsulates similar logic that occurs in several use cases is quite common.
For example, you may discover several use cases need the behavior to search for and then update information about students, indicating the potential need for an "Update Student Record" use case included by the other use cases.
Why should you bother maintaining an "Includes" and an "Extends" list in your use cases? The answer is simple: Yes, it would be nice if everyone has access to the use-case diagram because it also contains this information, but the reality is that sometimes you use different tools to document each part of your model.
For example, your diagrams could be drawn using a drawing package and your use cases documented in a word processor.
Some of your project stakeholders may have access to the word processor you are using, but not the drawing package. The main disadvantage of this approach is you need to maintain these two lists in parallel with the diagram, the danger being they may become unsynchronized. Inheritance Between Use Cases Use cases can inherit from other use cases, offering a third opportunity to indicate potential reuse.
Figure 1 depicts an example of this, showing that "Enroll Family Member in University" inherits from the "Enroll In University" use case. Inheritance between use cases is not as common as either the use of extend or include dependencies, but it is still possible. The inheriting use case would completely replace one or more of the courses of action of the inherited use case.
In this case, the basic course of action is completely rewritten to reflect that new business rules are applied when the family member of a professor is enrolling at the university. Family members are allowed to enroll in the school, regardless of the marks they earned in high school, they don't have to pay any enrollment fees, and they are given top priority for enrollment in the university.
Inheritance between use cases should be applied whenever a single condition, in this case, the student is a family member of a professor, would result in the definition of several alternate courses.
UML Use Case Extend
An include relationship points from the CheckOrderStatus use case to the LogIn use case to indicate that the CheckOrderStatus use case always includes the behaviors in the LogIn use case. The "extend" relationship is explained as follows: You are developing an e-commerce system in which you have a base use case called Place Online Order that has an extending use case called Specify Shipping Instructions.
An extend relationship points from the Specify Shipping Instructions use case to the Place Online Order use case to indicate that the behaviors in the Specify Shipping Instructions use case are optional and only occur in certain circumstances. So the key point in the extends relationship is "optional"! It adds further functionality to the base use case which may be restricted by constraints. The following diagram shows this: Consider the "Order Wine" and "Serve Wine" use cases.
The "Order Wine" extends the "Order Food", meaning that wine may be ordered by the customer, but not necessarily optional. Therefore the use case "Server Wine" has a condition on its extend relationship: The notation is a arrow with a white triangle at the end, basically the same that is used for defining the inheritance extends relationship in the UML class diagrams.Include relationship in use case diagram(In hindi ) by Hightech