Semantic Modeling And Automated Reasoning For Non-Functional Requirements Interaction

Non-Functional Requirements (NFRs) address important issues such as qualityproperties and performance for software systems, products or services. NFRs are vitalto the success of software system. Duo to the distinct nature from FunctionalRequirements (FRs), as subjectivity, relativity, diversity and interactivity, NFRsproblems are challengeable and currently acting as one of the hottest spot issues inrequirements engineering society. The works of this thesis are derived from projectsgranted by the National High Tech Program (863Program) and Nature ScienceFoundation of Chongqing. The thesis focuses on interaction problems of NFRs, a.k.a,harmony and conflict relationships among nonfunctional attributes of software system.As a methodology, Softgoal Interdependency Graph (SIG) from the well knownNon-Functional Requirement Framework is a graphical and structural modelinglanguage which is specialized to deal with NFRs interdependencies and interactions.SIG is an operative tool to model and visualize complex correlations among NFRs bypresenting a process-oriented support for NFRs refinement, trade-off and deign decision.Nevertheless, the disadvantages of SIG lie in the limitation of formalize and automation,lacing of syntactic and semantic interoperability for instance data models, as well asdifficulties of carrying out machine readability and automated reasoning.For the nature of NFRs problems, it is the reflection of system complexity andemergency. It is better to investigate NFRs with a systematic view to know the truth ofmechanism for harmony and conflict, to detect conflict as early as possible. Carryingout this task can help the developer to make decision with abundant facts for rationale.On the other hand, NFRs will be developed and implement as cross-cutting concernsamong multiple components, results in complex dependencies between NFRs and FRs.Consequently, it is essence to address the implicit correlations of NFRs which arecaucused by FRs interaction.The thesis aims to extent the capability of NFR Framework and SIG for modelingand analyzing NFRs, with the aid of Ontology and Semantic Web technologies. Thework also explores approaches to modeling NFRs in semantic level with the synergy ofontological axioms and semantic rules, to facilitate knowledge representation, semanticinteroperability, sharing and reusing of instance data models of NFRs. Furthermore, thethesis proposes formalized and ontological methods for modeling and representing NFRs interaction, as well as mechanism of harmony and conflicts. Thus leads us to a setof well defined semantic rules for automated reasoning with NFRs interaction. Thethesis contributes NFRs modeling and reasoning with five aspects, as follows.Firstly, the author proposes a formal and ontological approach to model NFRsinteraction, develops an NFRs core ontology represented with Web Ontology Language(OWL). The work starts with formalizing NFR framework and SIG which are acting asreference models for representing NFRs interaction. An Ontology Engineering processis performed then, in detailed means of concept hierarchy, attitudes derivation, patternsof modeling relations between/among NFRs, and axiomatization as well. AnOWL-based core ontology is developed to support conceptual modeling and knowledgerepresentation for NFRs.Secondly, the thesis investigates methods to represent an instance model of SIG,with analyzing its structural properties and syntactic interoperability, and exploresmeans of syntactic consistency checking as well as instance model metrics. The workbegins with an ontological analysis for knowledge-based framework of SIG to representNFRs interaction. By showing the axioms and restrictions of SIG as a strictlycircuit-less directed graph, the author discusses structural properties of softgoaldecomposition and correlation as interdependencies. Moreover, a set of structuralcharacteristics derived from Graph Theory is selected as metric factors for instancemodels. A group of semantic rules are defined then for automated reasoning, andvalidated by testing them with seven instance SIG models from literature.Thirdly, the thesis investigates and formalizes the mechanisms of NFRsinteractions as harmony and conflicts in SIG models, which are caused byinterdependencies of softgoals in the graph. The work begins with analysis of NFRssatisficing evaluation process, with semantic modeling for evaluation criteria. Therewith,the thesis proposes approach to correlation rules for implicit softgoal interdependencieswith domain knowledge, as well as rules for indirectly semantic correlation byextending so called delta evaluating method. A group of reasonable rules in SemanticWeb environment is defined as well, to facilitate analysis and detection of conflictsbetween/among NFRs in SIG instance models. An experimental study is performed then,to validate correctness of rules, and feasibility proposed methods.Fourthly, the thesis takes FRs into account, by extending currently method torepresent dependencies of NFRs and FRs in an incorporative model. We propose meanswith a set of correlation rules to detect NFRs conflict which are derived from FRs interaction. The start point of the work is to represent interdependencies of FRs andNFRs with a modeling language named F-SIG. Thus the author investigates andformalizes mechanisms of FRs interaction, proposes an ontological approach to detectFRs interaction with semantic rules. The rules for implicit correlations of NFRs causedby FRs interaction are presented then to detect potential conflicts of NFRs. A case studyon smart home system is performed, to validate the feasibility proposed methodsFinally, we put a knowledge based method for NFRs interaction into above works,with regarding to its properties as modularity, cross-cutting concerns, extendibility andreusability. The scattered works can also act as supplementary contributions for thethesis, to make the above works more feasible in real practice on NFRs problems.