Presentation about ifcOWL at the Summer School on Linked Data 4 Smart Cities, in Cercedilla (2015): http://smartcity.linkeddata.es/LD4SC/, organised by the Ontology Engineering Group of Universidad Politécnica de Madrid.

1. ifcOWL
an ontology for building data
Pieter Pauwels
Ghent University

2. WHAT IS BIM / WHAT IS IFC?

3. Building Information Modelling

4. ISO standard file format
• Industry Foundation Classes
• Managed by BuildingSMART
• Schema specified in EXPRESS information
modelling language
• Number of versions: IFC2X2 – IFC2X3 – IFC4

5. buildingsmart-tech.org

7. The EXP file

8. BUILDING AN IFCOWL ONTOLOGY
FOR DESCRIBING BUILDING DATA

9. 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

10. converting EXPRESS schema to OWL
IFC
Schema
Simple data type
Defined data type
Aggregation data type
SET data type --------
LIST & ARRAY data type --------
Constructed data type
SELECT data type --------
ENUMERATION data type --------
Entity data type
Attributes --------
Derive attr
WHERE rules
Functions
Rules
ifcOWL
Ontology
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
-
-
-
-

11. ifcOWL ontologies available
Ifc2x_all_lf.exp
IFC2X2_ADD1.exp
IFC2X2_FINAL.exp
IFC2X2_PLATFORM.exp
IFC2X3_Final.exp
IFC2X3_TC1.exp
IFC4.exp
IFC4_ADD1.exp
not supported
not supported
not supported
not supported
IFC2X3_Final.owl / .ttl
IFC2X3_TC1.owl / .ttl
IFC4.owl / .ttl
IFC4_ADD1.owl / .ttl
http://www.linkedbuildingdata.net/resources/IFC2X3_Final.ttl
http://www.linkedbuildingdata.net/resources/IFC2X3_TC1.ttl
http://www.linkedbuildingdata.net/resources/IFC4.ttl
http://www.linkedbuildingdata.net/resources/IFC4_ADD1.ttl

12. CLASSES INDIVIDUALS OJECT PROPERTIES

13. RESTRICTIONS

14. I WANT TO HAVE IFCOWL
INDIVIDUALS

15. Option 1 – Manual modelling from scratch
using an ontology editor

16. 1. Not all IFC restrictions (rules, derive
attributes, functions) available in
ifcOWL => no complete consistency
checking
2. Tedious and error-prone process
limitations

17. Option 2 – Automatic modelling from scratch
using 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);
}

18. 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

19. Option 3 – Conversion of existing IFC SPFF Files
Free open file-to-file conversion service: http://smartlab1.elis.ugent.be:8889/IFC-repo/

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

21. COMMUNITY EFFORTS

22. Joining / combining initiatives
W3C LBD Community Group BuildingSMART LD Task Force
linkedbuildingdata.net
www.w3.org/community/lbd/
…
linkedbuildingdata people
LDAC event

23. Thank you
pipauwel.pauwels@ugent.be