A Semantic modelling and automated reasoning of non-functional requirement conflicts in the context of softgoal interdependencies

Non-functional requirements (NFRs) address important issues in software systems, and are vital in successful software. The NFR problems in a system reflect the complexity of that system. Ideally, NFRs are systematically investigated to determine the aspects that may be harmonious or cause conflicts so that conflicts should be detected as early as possible. The work aims to extend the scopes of the NFRs framework and softgoal interdependency graph (SIG) for modelling and analysing NFRs. A formal ontological approach to modelling NFR interactions is proposed, and a core NFR ontology is developed in the ontology web language. The mechanisms involved in NFR interactions with SIG models (through interdependencies in the softgoals) are investigated and formalised. The NFRs are first analyses using a semantic modelling process to provide evaluation criteria. Next, correlation rules for implicit softgoal interdependencies are proposed from knowledge of the domain, and rules for indirect semantic correlations are proposed by extending the delta evaluation method. Reasonable rules in the semantic web environment are defined to allow conflicts between NFRs in SIG instance models to be detected and analysed. A concepts proof is performed to illustrate tool support of the proposed method, and validate the rules for conflict detection.