Software Architect's Handbook

Non-functional requirements

Non-functional requirements are conditions that must be met in order for the solution to be effective, or constraints that must be taken into consideration. Business analysts and other stakeholders tend to do a good job at capturing functional requirements, but they don't always focus as much on non-functional requirements. However, non-functional requirements are an important part of requirements engineering. The success of the project is dependent on the non-functional requirements and whether or not they are met.

When a software architecture is designed, the software architect must ensure that the non-functional requirements can be satisfied. Non-functional requirements can have a significant impact on the design ...