Example IFC Elements Selection Mappings

The following includes examples of different ways to map E3D elements to IFC Eeements – many others are possible.

An element mapping has an optional list of E3D element types, and also an optional Boolean expression. In many cases only one or the other is required, but in others both are needed.

Example

To distinguish between some E3D GENSEC elements which should be mapped to IfcBeam elements, and other that should be mapped to IfcColumn elements. Depending on how the structural model is defined, expressions may use text or geometric attributes such as:

• What is the Structural Classification of the section?

  STRUCL EQ 'BEAM'

• Are the Up coordinates of the two ends the same (a beam)?

  POSE[3] EQ POSS[3]

• Are the East and North coordinates of the two ends the same (a column)?

  POSE[1] EQ POSS[1] AND POSE[2] EQ POSS[2]

For E3D Equipment it may well be desirable to use expressions based on full or partial text attributes, for example the complete name of the E3D element:

namn eq 'Units-Heater'

• a partial name or description:

  MATCHWILD(Namn,'*METER*')

  MATCHWILD(Desc,'*Pump*')

  MATCHWILD(Namn,'*CONNECTION_BOX*') OR MATCHWILD(Namn,'ELECTRIC_JB_*')

• a UDA (these UDAs are examples, not recommendations)

  :EQUI_SUB_GROUP eq 'Space Heater'

  :EXPECTED_IFC_CLASS EQ 'IFCFLOWTERMINAL'

• For Piping, HVAC and similar, useful expressions can include attributes of the direct or indirectly owning elements, such as any element directly owned by a BRANCH

  ( TYPE OF OWNER EQ 'BRAN' )

• a combination - in this case selecting items directly owned by a branch of a pipe with a given UDA value, but excluding implicit tubing

  ( TYPE OF OWNER EQ 'BRAN' ) AND ( :HEAT_SYSTEM OF PIPE ) AND ( TYPE NE 'TUBI' )

• Supports, fixtures and fittings often have deeper hierarchies, perhaps including templates, so expressions including AHLIST (the list of the types of elements above the CE) can be useful, for example to map a STRU element which is directly or indirectly below a SUPPO element to an IfcElementAssembly

  'SUPPO' inset (AHLIST)

• Map STRU, FRMW and SBFR elements which have at least one member which is a Stairflight or a RungLadder to an IfcStair

  NOT ( UNSET ( MEM STRFLT ) AND UNSET (MEM RLADDR ) )

• AHLIST is also very useful in expressions where there is no Ifc element required (the Ifc Element name is omitted – meaning that matching items should be included in the same Ifc Element as their owner, or where the special value Exclude is used, in which case geometry and attributes of the matching element should not be exported at all). For example: elements directly or indirectly below a Temple should not be exported separately.

  'TMPL' inset (AHLIST)