Would anybody support an approach of getting IfcExcavation ?
Have a look at 220.127.116.11 IfcEarthworksCut - IFC18.104.22.168 Documentation
thank you. I think I would never have found that myself.
wait a minute. IfcEarthworkCut is the result, which is a feature of a terrain. But I am looking for the entity for the excavation is self. The Volume that is excavated from terrain needs to be filtert and measured in an QTO.
There’s probably a lot of nuance to this that I’m not understanding, but did you consider representing that then as an IfcTask? http://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcTask.htm
First: IfcEarthworksCut is a subtype of IfcFeatureElementSubtraction. This means that it:
A - Represents the void that is the result of the excavation. This void represents the excavated volume and may carry a QTO
B - Uses the VoidsElements relationship to reference the ground element/elements that are “voided”. These ground elements may carry e.g. material info.
For IFC Tunnel, we made some extensions to this structure.
- Adding an IfcExcavation supertype which has IfcFeatureElementSubtraction as its supertype. This means that the statements regarding “voiding” are still valid.
- Making IfcEarthworksCut a subclass of IfcExcavation for cases where the excavation is “open”
- Adding IfcUndergroundExcavation as a “sibling” to IfcEarthworksCut for the cases where the excavation occurs “underground”.
If you by “the entity for the exavation itself” mean the physical thing (the excavation body), then use either IfcEarthworksCut or IfcUndergroundExcavation. The way I am reading the question, this allows you to filter out the excavations with their quantities and possibly also the properties of the ground that was excavated. If not, can you please clarify?
If you instead mean the process of excavating, then this should probably be some kind of IfcProcess (IfcTask?) as stated above.
Thank you Lars.
I am not talking about the process, but the volume that is excavated, when producing the cut that is the void in the terrain. For buildings this volume has to be measured (quantified). That volume needs to have the surface of the surveyed terrain.
It has to be delivered a separated element.
For my understanding it could be a subelement or PreDefinedType for IfcOpening or IfcGeographicElement. Actually it is a very huge recess in the terrain.
Anyway, software vendors have to be advised to provide a IfcTyp for it.
To me it sounds like IfcEarthworksCut (in IFC 4.3) or IfcUndergroundExcavation (in Ifc 4.4) are the elements you are looking for. They represent “the cut that is the void in the terrain” as you state. Btw, you also mention IfcOpening(Element). This is another sibling to IfcExcavation (subtype of IfcFeatureElementSubtraction). So IfcEarthworksCut/IfcUndergroundExcavation are very similar concepts, but specifically made for excavations which seems to me like the thing you are looking for.
In my opinion the way to approach this (or any other proposed data modeling extension in the IFC schema) would be to step back and apply a decision tree based on the schema hierarchy, such as:
- IS the proposal a Process OR a Product (OR a Control, a Property, a …)?
- DOES it need new/unique classification OR can it be represented as an Enumeration of an existing class?
- IF it is unique and a Process, is it a single Event, a Procedure composed of Tasks, OR a Task?
- IF it is unique and a Product, is it an Element, or a Spatial Element (OR a Port, a …)?
- IF it is a Product, is it a single Object OR a Group OR Assembly of Objects?
I think if you start here, at the higher level, then you can deal with the other questions of dependencies and relationships to other classes that need to be answered.
Just to provide information about current state-of-the-art.
In IFC 4.3, there is already an element (IfcEarthworksCut) defined according to what I wrote above.
For IFC 4.4, this structure is proposed to be extended to better cover the needs for underground excavations which means that a sibling (IfcUndergroundExcavation)) to IfcEarthworksCut is proposed and that a common ancestor (IfcExcavation) for these two entities is introduced.
Hopefully this covers the needs stated. It is the result of the work of the IFC Infra/Rail projects and the IFC Tunnel project.