[ Fail on GRF001 ]

[michelangelo-acca]

Can someone explain why this file fails on GRF001?

grf001_4x3_geo.zip

[evandroAlfieri]

Hi @michelangelo-acca , sorry for the late reply (Implementers Assembly). We'll look into it and come back asap

[aothms]

Hi @michelangelo-acca . There are two geometric representation contexts in the model:

#19=IfcGeometricRepresentationContext('3D','Model',3,1.E-4,#20,#22)
#146=IfcGeometricRepresentationContext($,'Plan',3,1.E-4,#147,#148)

Only the first one has a IfcMapConversion assigned:

#205=IfcMapConversion(#19,#206,427794.150823833,4524155.13101531,97.,5.33965490548146E-1,8.455062713568E-1,1.)
                      ^^^

So the coordinate operations on these are not identical.

[michelangelo-acca]

Hi @michelangelo-acca . There are two geometric representation contexts in the model:

#19=IfcGeometricRepresentationContext('3D','Model',3,1.E-4,#20,#22)
#146=IfcGeometricRepresentationContext($,'Plan',3,1.E-4,#147,#148)

Only the first one has a IfcMapConversion assigned:

#205=IfcMapConversion(#19,#206,427794.150823833,4524155.13101531,97.,5.33965490548146E-1,8.455062713568E-1,1.)
                      ^^^

So the coordinate operations on these are not identical.

But does this means that we need to have multiple MapConversion(s) in the same file, even if they are the same? One for each Geometric Context?

[aothms]

I'd say so. Similar to how these context have the same-valued WorldCoordinateSystem and north vector.

#19=IfcGeometricRepresentationContext('3D','Model',3,1.E-4,#20,#22)
  #20=IfcAxis2Placement3D(#21,$,$)
  #22=IfcDirection((0.,1.))
#146=IfcGeometricRepresentationContext($,'Plan',3,1.E-4,#147,#148)
  #147=IfcAxis2Placement3D(#21,$,$)
  #148=IfcDirection((0.,1.))

Alternatively you could make the 2nd context a subcontext of the 1st one. But I personally don't know enough about the agreements to know whether that's a good or bad recommendation.

Because without the coordinate operations explicitly agreeing you're essentially saying that their representations are effectively on a different place on the map. (Which to me shows we shouldn't have equated context with positioning, but there is a long history going back to that).

[Ghesselink]

Alternatively you could make the 2nd context a subcontext of the 1st one. But I personally don't know enough about the agreements to know whether that's a good or bad recommendation.

This will indeed cause the GRF001 rule to pass.

Furthermore, in the schema, the attribute for coordinate operations in the context is allowed to be empty. Currently, for GRF001, this will be permitted only if (1) there is only one context, or (2) the attribute is empty for all contexts within the file. Is this the desired behavior?

The feature description is already updated

[evandroAlfieri]

@michelangelo-acca is the explanations above clear enough? Can we close this issue or do you see the need for follow up actions?