The role of quality requirements in software architecture design

An important issue during architectural design is that besides functional requirements, software architecture is influenced greatly by quality requirements, which often are neglected. The earlier quality requirements are considered, the less effort is needed later in the software lifecycle to ensure a sufficient software quality levels. Errors due to lack of their fulfilment are the most expensive and difficult to correct. Therefore, attention to quality requirements is crucial during an architectural design. The problem is not only to gather the system''s quality requirements, but to establish a methodology that helps to deal with them during the software development. To alleviate the problem, this paper lays out important concepts and notions of quality requirements in a way they can be used to drive design decisions and evaluate the architecture to estimate whether these requirements are fulfilled.