Tuesday, April 08, 2008

Prioritize your non-functional requirements

Non-functional requirements (like usability, security, performance, fidelity) are important success criterions in software architecture and development. It is a misconception that all requirements can be covered by functional requirements. Many requirements are of twofold nature, say security, that typical consists of functional and non-functional types. If this has been recognized and accepted, prioritization is the next important step. It should be not acceptable to have TWO non-functional requirements (also known as Quality Attributes) with the very same high level of priority. This is a critical contradiction that must be communicated and resolved. If not, you might be end with a beast that is highly secured and comfortable to use (let’s call it digital monkey wrench) – which is basically not feasible. It is always a challenge to make compromises for each Quality Attribute and to communicate and explain this. Utility Trees are a great tool to list, depicts and prioritize non-functional requirements.

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