general comments PROPS ontology and options in converter

[mathib]

(not sure where to post this regarding the RWTH Aachen PROPS ontology, as I could not find any public repo online. Please move this accordingly if needed!)

Just noticed that the LBD output graphs of the converter contain URIs for the properties in a PROPS ontology of the RWTH Aachen, which is a good step forward. Some comments, questions and suggestions though regarding PROPS:

• I've noticed that for each property, the "regular" (owl:ObjectProperty) and "simple" (owl:DatatypeProperty) are available, but the latter is erroneously typed as owl:ObjectProperty instead of owl:DatatypeProperty. Can this be corrected?
• Continuing, a link between both "regular" and "simple" properties would be useful, e.g. through the use of a new owl:AnnotationProperty. Having such a link will make it easier for users to jump between property levels as required for their use cases (e.g. downgrading all L3 properties in a dataset to L1, as that would be easier to reuse by a receiving party). Example: props:withLock ex:equivalentSimpleProperty props:withLock_simple (benefit: no need anymore for string operations in SPARQL when you want to switch levels as you can query the PROPS ontology for this info)
• The PROPS ontology is very long, and difficult to use as all content is served in one static RDF file. A better alternative would be to split it in multiple RDF files per IFC pset (probably requires a switch from hash URIs to slash URIs). In addition, to ease the access to the PROPS, the entire RDF could be served through a Triple Pattern Fragment server or SPARQL endpoint. With a data service available, users are able to fetch the specific data they need.
• The rdfs:isDefinedBy already links to another RDF file per pset, but the URIs used there do not contain the ones from RWTH Aachen (e.g. http://lbd.arch.rwth-aachen.de/ifcOWL/IFC4-PSD/Pset_FurnitureTypeFileCabinet#p38e5e080d1e911e1800000215ad4efdf does not contain http://lbd.arch.rwth-aachen.de/props#withLock but http://linkedbuildingdata.net/ifcOWL/IFC4-PSD/Pset_FurnitureTypeFileCabinet#WithLock
• Please provide ontology metadata in the PROPS ontology, such as a license! Useful examples for ontology metadata are provided by Widoco and LOV

Besides the properties that are based on IFC propertysets, the IFC attributes are not yet covered in the RWTH Aachen PROPS ontology? Will this be tackled in the future?

In IFC models, people can also create their own custom properties in their own custom property sets. A nice feature request for the IFCtoLBD converter, would be to allow users to provide a mapping file to transform their custom IFC properties (strings) into the correct URIs that are defined in an ontology available elsewhere outside IFC.