EXPRESS to OWL for construction industry: Towards a recommendable and usable ifcOWL ontology

• The added value of an ifcOWL ontology is outlined.
• The key characteristics of the EXPRESS data modelling language are documented.
• A procedure is proposed to convert the IFC EXPRESS schema to an ifcOWL ontology.
• Indications are provided of how RDF graphs can be built with this ifcOWL ontology.
• The proposed procedure and results are compared in detail with existing proposals.

An increasing number of information management and information exchange applications in construction industry is relying on semantic web technologies or tools from the Linked Open Data (LOD) domain to support data interoperability, flexible data exchange, distributed data management and the development of reusable tools. These goals tend to be overlapped with the purposes of the Industry Foundation Classes (IFC), which is a standard for the construction industry defined through an EXPRESS schema. A connecting point between semantic web technologies and the IFC standard would be represented by an agreed Web Ontology Language (OWL) ontology for IFC (termed ifcOWL) that allows to (1) keep on using the well-established IFC standard for representing construction data, (2) exploit the enablers of semantic web technologies in terms of data distribution, extensibility of the data model, querying, and reasoning, and (3) re-use general purpose software implementations for data storage, consistency checking and knowledge inference. Therefore, in this paper we will look into existing efforts in obtaining an ifcOWL ontology from the EXPRESS schemas of IFC and analyse which features would be required in a usable and recommendable ifcOWL ontology. In making this analysis, we present our implementations of an EXPRESS-to-OWL converter and the key features of the resulting ifcOWL ontology.