And when possible use minimum relationships in your use case diagrams. Īnd discount is "optional" based on a condition so "extend" is also technically legal.īut you have unnecessary lines, which I do not understand.ĭo not waste your time on Use Case Diagrams to much.The important thing is use case scenarios. And this step is also repeating by Pay Late Fee use case. ![]() An extend relationship indicates that one use case is a variation of. The "Rent video" and "Charge credit" card relationship is technically legal since it is said that Rent Video use case include "Charge Credit" : In order to rent a video you should always charge credit card. A use case generalization shows that one use case is simply a special kind of another. Use Case Modeling,Kurt Bittner Ian Spence or Patterns for Effective Use Cases, Steve Adolph, etc. If wanted to get more info Check Chapter Using Generalization between Use Cases of the book It is interpretation is somehow problematic. Generalization: represents the relative difference in abstraction level between the two use cases. If you are a novice modeller stay away from Generalize Relationship. But if you think optional behavior is important and should be seen on use case diagram, then show it on diagram with extend relationship But many times, while you are writing your use cases, you have a Extensions sections and without showing extend relationship in a diagram, you can just record-write optional behavior in that sections. ![]() You have an optional behavior in use case base based on a condition. Or you may use "include" relationship to decompose a long use case into smaller sub units. A Senior Consultant can do all that a Consultant can do, but can also initiate consultancy project and conclude consultancy project and Invoice customer. then extract repeating steps a separate use-case, then reference it from the other use cases using "include" relationship. Draw a use case diagram of a system showing a Consultant who can record consultancy visits and consultancy expenses. For the most part, the popular text books on UML introduce the include relationship but give little useful guidance on the extend and the generalisation relationships. While you are writing use cases, if you see that some steps in use case scenarios, occur again and again. Introduction UML defines three stereotypes of association between Use Cases, include, extend and generalisation. You do not have to ( and should not) write all of them in details. So instead of asking "is it okay to use use this relationship or not, first write your use case scenarios. Use Cases are text stories which shows interaction of "actors" with system in order to reach a "goal". ![]() In Use Case Diagram, between use cases, you can define 3 relationships: Use cases (for example, wash dishes and service dishwasher) represent expectation for a system from a user perspective. On the UML Diagram the Generalization association represents as the line with empty triangle that connects superclass and subclass. First let's give right name to this relationships: case diagrams depict generalization relationships between use cases The product does not generate code for use-case diagrams.
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