defintion of facet

[volkerkrieger]

Please provide a defintion of _facet (pls not by stating examples)

[Moult]

https://github.com/buildingSMART/IDS/blob/development/Documentation/UserManual/specifications.md#how-specifications-can-describe-information

[volkerkrieger]

Studying this documentation i still miss a clear definition of the facet concept as i am used to from my work in ISO and CEN standardization. But i have tried to work out one:

[volkerkrieger]

where i might be wrong (Entity Facet does not include IfcRelationships...)

[aothms]

The PartOf facet relates indeed to objectified relationships, but:

• (a) only considers a specific set of relationships: https://github.com/buildingSMART/IDS/blob/6705c99036ad7caba62679dbe56c81c87b53fa5b/Documentation/UserManual/partof-facet.md
• (b) considers the other end of the relationship, not the relationship itself. In case of [Wall] <- RelDecomposes -> [Part]. The PartOf facet allows to filter/constrain only those Parts that have a role in a decomposition relationship with Wall. For example.

Technically speaking the entity facet can govern all IFC entity types (e.g Materials, Relationships, Property) and use the Attribute facet e.g to constrain something abt their attributes. But the semantics might be different. E.g the Property facet also considers inheritance rules with Occurence-Typeobject relationship and uses specific mechanisms for traversing properties associated to Materials/Profiles/Elements/TypeObjects which all use a different attribute (inverse or forward) in the schema to asssociate properties. The attribute facet is looking strictly at the attribute of that particular instance.

[volkerkrieger]

yes . matthias weise also told me just now .. i will correct....

[volkerkrieger]

[volkerkrieger]

also as table

[andyward]

Just a quick clarification on this table:

The IDS Entity facet can apply to more than simply classes of IfcElement and IfcElementType. The Entity facet can be used with any IFC Entity and so could include thinks like Spatial Elements and concept such as IfcProcess, and can even be employed to specify non-rooted entities like IfcActor, IfcMaterial etc.

In the same way, the Attribute facet can be used on any Ifc Entity, not just Elements/Types

I'd also note that the Property Facet has another parameter: datatype, which specifies the property's IFC datatype / measure.

[volkerkrieger]

Thank You very much, Andy. I appreciate these comments since i am writing an English-German 2-column version of the IDS specification (BuildingSMART is not a Standards body ...) for my clients.

Does that mean that the entity facet of IDS is based upon the list of entities as in ISO 16739:2024 (IFC 4x3) Annex B.1 (Alphabetical Entity listing)? This would also include the resource schema.... and extend the application of that facet largely but reasonably..

[andyward]

Does that mean that the entity facet of IDS is based upon the list of entities as in ISO 16739:2024 (IFC 4x3) Annex B.1 (Alphabetical Entity listing)? This would also include the resource schema.... and extend the application of that facet largely but reasonably..

I believe any IFC entity for the IFC schema is permitted. So yes you can test entities in essentially all the IFC domains. If in doubt I'd recommend testing your IDS with the IDS Audit tool or you can check IDS files at https://www.xbim.it/ids - which uses the same tool.