What is precondition and postcondition in use case?
A precondition is the state of the system and its surroundings that is required before the use case can be started. A postcondition is the states the system can be in after the use case has ended.
What is precondition in UML?
OCL provides special syntax for specifying pre- and postconditions on operations in a UML model. Pre- and postconditions are constraints that define a contract that an implementation of the operation has to fulfill. The USE tool allows to validate pre- and postconditions by simulating operation calls.
What is the difference between a precondition and a trigger?
Preconditions – what must be true or happen before and after the use case runs. Triggers – this is the event that causes the use case to be initiated. Main success scenarios [Basic Flow] – use case in which nothing goes wrong.
What is Subflow in use case description?
A subflow can be thought of as an “internal include”. The difference between an alternative flow and a subflow is that alternative flows insert themselves into another flow. The flow it inserts itself into has no knowledge of the alternative flow. An alternative flow may also resume at any place within the use case.
What do use case exceptions represent?
What do use case “exceptions” represent? The purpose of exceptions in use-case is to identify some of the situations that are not covered in the preliminary use case. The situations that are identified in exceptions are covered while refining the preliminary use case.
What is assumption in use case description?
An assumption is a state that must be reached before the Use Case can be performed, but does not constitute an actual precondition of this Use Case, and is not specifically included in the Flow of Events.
How can a nonfunctional requirement be described in a use case model?
Non-functional requirements are often categorized as usability-, reliability, performance, and substitutability-requirements (see also Concepts: Requirement). They are often requirements that specify need of compliance with any legal and regulatory requirements.
Which all of the following are the elements of the use case specification?
Use case diagram components
- Actors: The users that interact with a system. An actor can be a person, an organization, or an outside system that interacts with your application or system.
- System: A specific sequence of actions and interactions between actors and the system.
- Goals: The end result of most use cases.
How do you write pre and post conditions?
1 Answer
- Pre-conditions are the things that must be true before a method is called. The method tells clients “this is what I expect from you”.
- Post-conditions are the things that must be true after the method is complete.
- Invariants are the things that are always true and won’t change.