Friday, July 04, 2008

Handling Non-Functional Requirements with Utility Trees

I would like to pick up the topic Non-Functional Requirements (aka Quality Attributes) briefly. The topic is understood and accepted widely but the handling lacks clear methodology, structure and tools. Utility Trees are a good approach to overcome this. A Utility Tree contains Utility as the root node. The second level nodes are the quality attributes which are identified for the software system; in my tiny example: security, performance and availability. Btw, the example is about an e-commerce solution where payment is involved. Sure, extensibility/modifiability should be added as another quality attribute. We-based applications are subject for continuous change. Each of the quality attributes has specific concerns, in this example two per quality attribute. In the next level (just sketched in my example), scenarios are the leaves of the utility tree. They are typical prioritized along two dimensions – importance to the success of the system and identified risk in achieving the objective. Prioritization is based on a ranking using Low [L], Medium [M] and High [H]. I have just added two scenarios to my example; both are about performance. How to move forward with the utility tree? This will be covered in one of my upcoming post. Have great weekend!

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