Deprecating layers

[SergejMuhic]

These are, in my view, a bit outdated concepts. They do have a place in assigning styles, so maybe merge IfcPresentationLayerAssignment and IfcPresentationLayerWithStyle?

[TLiebich]

I would opt for removing IfcPresentationLayerWithStyle- as of IFC4 it is deprecated to use it for applying style (colour), in order to reduce the already too many different ways to do so. So it should not be used anymore.

IfcPresentationLayerAssignment- although one can argue that the time for CAD layers has long passed, they are still used in practise. Maybe we need to keep it?

[jwouellette]

This is an excellent example of something that needs further discussion and feedback from the ISG members... who will be meeting in a week’s time.

A reminder that the other issues will need their input as well.

On Thu, Mar 5, 2020 at 7:48 AM Thomas Liebich notifications@github.com wrote:

I would opt for removing IfcPresentationLayerWithStyle - as of IFC4 it is deprecated to use it for applying style (colour), in order to reduce the already too many different ways to do so. So it should not be used anymore.

IfcPresentationLayerAssignment - although one can argue that the time for CAD layers has long passed, they are still used in practise. Maybe we need to keep it?

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[TLiebich]

@jwouellette - sure, and this applies to all - we should not decide major steps without getting back to our "customers", the software industry, first.

[berlotti]

All of the issues in this repo need active involvement from implementors. Inside and outside ISG.

[SergejMuhic]

I would opt for removing IfcPresentationLayerWithStyle- as of IFC4 it is deprecated to use it for applying style (colour), in order to reduce the already too many different ways to do so. So it should not be used anymore.

IfcPresentationLayerAssignment- although one can argue that the time for CAD layers has long passed, they are still used in practise. Maybe we need to keep it?

I cannot remember seeing an IFC file with layers for quite some time now. I assumed they might be used for assigning styles still. So, yes I agree, this is a topic to be discussed.

[HerbertDobernig]

@TLiebich bS is supported by different stakeholder-groups, not only by software industry. I aggree that major steps need alignment with software industry to ensure feasibility and consensus. But please keep on with visionary and courageous proposals to ensure progress and to declutter outdated parts of the concept. Prominent supporters of bS expect significant progress to justifiy their contributions, I have heard. We need a good compromise between sufficient progress and economic viability.

[stefkeB]

Every ifc file I have seen from any of the major BIM authoring tools supports this. Many viewers provide a tree view to use them. I don’t see any particular reason to remove them. It is useful to transfer a part of the information in these applications via ifc. Even Revit which does not rely on layers transmits layers using its CAD mapping.

[TLiebich]

As a conclusion, I would propose to remove IfcPresentationLayerWithStyle, but keep IfcPresentationLayerAssignment. The second is still used today on a daily basis, see also @stefkeB comment, the first is outdated and should also be removed in order to simplify the styling (coloring) of components.

[TLiebich]

check list for removing IfcPresentationLayerAssignment

what do we win

• less redundency and less variations for assigning style information to shapes

what do we loose

• nothing

schema impact

• minor (essentially updating documentation)

instance model impact

• none

backwards compatibility impact

• none (does not change), for old files easy downcasting to supertype IfcPresentationLayerAssignment

automatic migration possible

• yes