Assumptions

[achen]

Just had a discussion about use case assumptions. These are always hard because it is hard to think about things that you have already assumed. On the other hand, assumptions are what kill projects.

How do you distinguish between assumptions and preconditions when writing use cases?

[MTalbot]

I think assumptions are things that you "generally think true", while preconditions are things that are fairly specific to your use case.

[jbeatty]

Pre-conditions are evaluated at run-time.
Assumptions are dealt with when planning and developing the system.


Preconditions - states that the system must be in before you start the use case.

Assumptions - things that are assumed to be true about the system (or about another system) for the use case/system to function.

In the case of assumptions, if one is not met, then it's not about picking a different use case to execute or a path through a use case, it's about changing your requirements for the system.

Example:
Pre-condition: User is logged in
Assumption: Authentication functionality already exists in the Account Management system and will not be developed in this system (which might be outside the scope of this system).

[JGrapes]

Pre-conditions are evaluated at run-time.
Assumptions are dealt with when planning and developing the system.

Preconditions - states that the system must be in before you start the use case.

Assumptions - things that are assumed to be true about the system (or about another system) for the use case/system to function.


I've recently been discussing this with some people, and I think jbeatty did a great job of distilling the difference!