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Showing posts from May, 2011

The problem with use cases

The greatest benefit I get from use cases is that they focus on the user. Use cases help me to think about what the user wants to do instead of only focusing on implementation details.

The biggest problem I have with use cases is that they are not structured. They are basically free text. For instance, if we have a use case Withdraw money from ATM, we may define that it has a precondition that Open account is performed, but we don't get any help from the method to see that.

What happens if someone later changes the Open account use case or defines a Close account use case? How do we find which other uses cases that need to be modified? We can look through the old use case diagrams and find dependencies, but I can almost guarrantee that these dependencies have not been maintained after they were initially created.

The solution to this is to connect the use cases to an object model. I don't mean a use-case realization with view and controller objects like ATM_Screen and ATM_Sess…

Getting the requirements right with object cases

One of the biggest problems in software projects is poor requirements. We always seem to misunderstand what the user is really trying to do or discover some missing functionality at the end of the project. Agile methods reduce this problem with short feedback cycles to discover misunderstandings early, but it would be even better to get rid of the misunderstandings before implementation.

Two things that really help me in this area are examples and objects. This article describes how to combine these with a method I am calling object cases.

An object case is an example of a user function connected to domain objects. It consists of 4 parts:
Initial objectsInputOutputResult objects
A typical week using object cases can be as follows:
Monday morning: Go through new functionality with the client.Monday afternoon: Planning and estimation.Tuesday: Implement automatic tests.Wednesday - Friday: Implement the actual functionality. My experience is that object cases help us a lot in all this activ…