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Proposal: Permit dataType equivalents for non-measure Property values

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#331 8 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
30/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
csharp
Domain
data

Research direction

Start with Documentation/facet-configurations.md and Documentation/DataTypes.md, then read the unresolved alternatives and comment history. Determine and document the agreed rule for equivalent non-Measure dataTypes, including whether the Audit tool is affected. Done means the rule, related documentation, and verification behavior have an explicit, tested outcome.

Written by the indexing model from the issue text.

Description

discuss & decide

According to the docs, dataType is a required field when specifying a value.

The implication of this is that the IDS author must know the correct IFC dataType expected for a property. For IfcMeasures this is no doubt important due to Units etc, but for a lot of simple cases this constraint feels overly prescriptive.

For instance an IDS author will now need to specify if a custom property called 'Acme_Reference' has a dataType of IFCTEXT, IFCLABEL, IFCIDENTIFIER or some other datatype. If the IFC exporter doesn't follow these conventions the IDS value check will fail, despite the value matching, and all these IfcTypes being backed by the same EXPRESS STRING type. In any upstream service processing this IFC the property will almost certainly be treated as the same String type so it will feel like a 'false negative' to a typical user.

i.e. To all intents and purposes these are the same to an end user - despite a different semantic:

#10=IFCPROPERTYSINGLEVALUE('Acme_Reference',$,IFCLABEL('Bar'),$);
#11=IFCPROPERTYSINGLEVALUE('Acme_Reference',$,IFCIDENTIFIER('Bar'),$);
#12=IFCPROPERTYSINGLEVALUE('Acme_Reference',$,IFCTEXT('Bar'),$);

I see a couple of options:

  1. Make dataType optional again (and update the Audit tool)
  2. Allow some limited aliasing between dataTypes at verification

The latter would be my suggestion. My thoughts would be to allow any non-Measure dataType to be deemed equivalent if it's underlying 'Type' is the same. I'd suggest for 99% of cases this is going to types backed by 'string'. You could also make the case that dataTypes such as IfcInteger and IfcPositiveInteger are equivalent but that's perhaps a more subtle edgecase.

Any thoughts?

Dominant language
C#
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