Software reverse engineering (SRE) plays a crucial role in contemporary software environments. Software developers may implement a system first then use SRE tools to generate design content such as the Unified Modeling Language (UML) diagrams. In the literature of SRE, studies mostly focus on how precisely the conversion can reflect the system, there is, however, little or no research that further looks into the quality of the converted results. Therefore, this paper presents an online knowledgebased ontological SRE system, OntRECoh, for quality evaluation of converted UML structural models. OntRECoh features a domain-specific knowledge base that focuses on cohesion design and a rule-based inference engine for rating the cohesion scores of a tested system that is written in Java code and providing improvement recommendations through its Web-based interface. Furthermore, in the work of evaluation, OntRECoh measures both static and dynamic cohesion of the tested system that addresses not only the design aspects but also the implementation aspects, for the evaluation to be more comprehensive and synthetic in the SRE context.