Reasoning nonfunctional goals and features in Web systems

The analysis of system\´s requirements supported by goals has lead us to define two classifications of goals, agent-centered, corresponding to four branches of our verbs goals ontology and object-centered, which is arranged in accordance with the stages of the object\´s lifecycle. In this work we show the pertinence and usefulness of the two classifications for nonfunctional requirements. The categories in both classifications are validated with about 200 nonfunctional features mentioned in the current approaches. This goal-based approach integrates functional and nonfunctional requirements from the earliest phase of system development, supporting the reasoning and elicitation of requirements. The nonfunctional categories defined for Web applications are illustrated with nonfunctional feature typologies for a Web system incorporating the \´\´usability" feature.