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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. The states described by pre- or postconditions should be states that the user can observe.
What is the purpose of precondition?
A precondition is a prerequisite. It’s the thing that has to happen before something else happens. For example, as a precondition to getting your allowance, you might have to give the dog a hairdo once a week.
How do you determine a precondition?
In computer programming, a precondition is a condition or predicate that must always be true just prior to the execution of some section of code or before an operation in a formal specification.
Who is responsible for ensuring that the pre-conditions are valid?
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Who is responsible if this inadvertently causes a 40-day flood or other disaster? The programmer who calls a function is responsible for ensuring that the precondition is valid.
When to use preconditions in a use case?
As you start to realize your use cases as sequence or activity diagrams, for example, the preconditions give you some clue that a check may need to happen in the software, maybe necessitating a call to some other operation/module/class.
When to use pre-conditions and post-conditions?
Each use case is only one part of a complete system. When certain behaviors must be handled by another use case prior to allowing anyone to access this use case, specify these conditions as assumptions. For example, verify that the user has permission to access this feature.
Which is an example of a pre condition?
For example, verify that the required parameters were passed and are valid. Assumptions and pre-conditions also define precedence among use cases. Use case precedence in turn supports screen and workflow design by defining the order in which use cases must be executed.
What’s the difference between preconditions and triggers?
Documenting preconditions and triggers is important to validating the completeness of use cases and requirements. There are subtle differences between them. Preconditions are promises that describe the state of the system prior to initiating the use case. Preconditions are mandatory. Triggers are events that cause a use case to be initiated.