ifcOWLan ontology for building data

Pieter PauwelsGhent University

WHAT IS BIM / WHAT IS IFC?

Building Information Modelling

ISO standard file format

• Industry Foundation Classes• Managed by BuildingSMART• Schema specified in EXPRESS information

modelling language• Number of versions: IFC2X2 – IFC2X3 – IFC4

buildingsmart-tech.org

The EXP file

BUILDING AN IFCOWL ONTOLOGY FOR DESCRIBING BUILDING DATA

Towards a recommendable and usable ifcOWL ontology

• When: 2nd half of 2014 • Who: Pieter Pauwels (Ugent) and Walter Terkaj (ITIA-CNR)• What: distill ONE recommended conversion procedure for converting an

EXPRESS schema into an OWL ontology, based on earlier efforts.• Results:

– Conversion procedure documented in article manuscript and separate slideshow

– Implemented in JAVA (https://github.com/mmlab/IFC-to-RDF-converter/tree/BS) and C++ converter

– Resulting ontologies:• http://linkedbuildingdata.net/resources/IFC4_ADD1.owl• http://linkedbuildingdata.net/resources/IFC2X3_TC1.ttl

converting EXPRESS schema to OWLIFC

Schema

Simple data type

Defined data type

Aggregation data typeSET data type --------

LIST & ARRAY data type --------

Constructed data typeSELECT data type --------

ENUMERATION data type --------

Entity data typeAttributes --------

Derive attrWHERE rules

FunctionsRules

ifcOWLOntology

owl:class + owl:DatatypeProperty restriction

owl:class

owl:class-------- owl:ObjectProperty restriction on ifc:hasSet-------- indirect subclass of ifc:List

owl:class-------- owl:unionOf ( owl:classes )-------- one of ( owl:NamedIndividuals )

owl:class-------- object properties

----

More details

in separate

presentation

ifcOWL ontologies available

Ifc2x_all_lf.expIFC2X2_ADD1.expIFC2X2_FINAL.exp

IFC2X2_PLATFORM.expIFC2X3_Final.expIFC2X3_TC1.exp

IFC4.expIFC4_ADD1.exp

not supportednot supportednot supportednot supportedIFC2X3_Final.owl / .ttlIFC2X3_TC1.owl / .ttlIFC4.owl / .ttlIFC4_ADD1.owl / .ttl

http://www.linkedbuildingdata.net/resources/IFC2X3_Final.ttlhttp://www.linkedbuildingdata.net/resources/IFC2X3_TC1.ttlhttp://www.linkedbuildingdata.net/resources/IFC4.ttlhttp://www.linkedbuildingdata.net/resources/IFC4_ADD1.ttl

CLASSES INDIVIDUALS OJECT PROPERTIES

RESTRICTIONS

I WANT TO HAVE IFCOWL INDIVIDUALS

Option 1 – Manual modelling from scratchusing an ontology editor

1. Not all IFC restrictions (rules, derive attributes, functions) available in ifcOWL => no complete consistency checking

2. Tedious and error-prone process

limitations

Option 2 – Automatic modelling from scratchusing APIs

im = ModelFactory.createDefaultModel();im.setNsPrefix("ifcowl", ontNS);im.setNsPrefix("inst", baseURI);for (int i = 0; i < inst.getList().size(); i++) {

OntClass cl = ontModel.getOntClass(ontNS + typeName);Resource r = im.createResource(baseURI + typeName + "_" + inst.getLine_num(), cl);

}

1. Not all IFC restrictions (rules, derive attributes, functions) available in ifcOWL => no complete consistency checking

2. Need to build modelling application anew, relying on a different software library at the basis

limitations

Option 3 – Conversion of existing IFC SPFF Files

Free open file-to-file conversion service: http://smartlab1.elis.ugent.be:8889/IFC-repo/

1. Two distinct applications, two distinct models -> versions can go out of control2. The converter can become a bottleneck

limitations

COMMUNITY EFFORTS

Joining / combining initiatives

W3C LBD Community Group BuildingSMART LD Task Force

linkedbuildingdata.net

www.w3.org/community/lbd/

…

linkedbuildingdata people

LDAC event

Thank you

pipauwel.pauwels@ugent.be