Ontology-based representation of IFC EXPRESS rules: An enhancement of the ifcOWL ontology

Semantic Web technologies are becoming more and more appealing to the community of the Industry Foundation Classes (IFC) users. The recent actions towards the development of an OWL version of the IFC schema (named ifcOWL) evidence the effort of facing the community request to specify IFC in an ontology language. This paper presents an enrichment of the EXPRESS to OWL conversion patterns with OWL class expressions that specifically capture certain constraints of the IFC standard. The presented class expressions can be used to improve the robustness of ifcOWL and support data integrity, consistency, and applicability across various scenarios of industrial application. In particular, the rules defining the relationships between non-abstract subtypes of IfcObject and corresponding subtypes of IfcTypeObject are analyzed and converted into novel class expressions. The proposed additions to the conversion pattern have been implemented into a software tool and the resulting ontology was tested against a use case to show the benefits of the new solution with respect to a basic ifcOWL. The novel conversion pattern enhances usability of the ifcOWL ontology by enabling its direct instantiation, without necessarily going through the intermediate generation of a STEP physical format that is then converted into an ontology.