4.1.3 Group Assignment

Group Assignment established an arbitrary collection of objects within a group. The grouping relationship does not apply any other meaning then grouping objects under some aspect. It is non-hierarchical, that is objects can be grouped into different logical groups, and it does not interfere with other relationship concepts, such as ObjectAggregation.

The Group Assignment concept establish a given object as being the group collection for other objects. An IfcZone is a specific group object for collecting spaces, IfcDistributionSystem is a specific group object for collecting distribution elements. Usually a grouping relationship is applied to group elements for a particular purpose or function. It usually implies the existence of a grouping relationship and the provision of some identity under which the group is characterized.

• Group collection is handled by an instance of IfcRelAssignsToGroup, which assigns all group members to the IfcGroup being the collection.
• Objects included in group as collected items are linked by IsGroupedBy pointing to IfcRelAssignsToGroup

NOTE  The IfcGroup maybe not yet have a grouping relationship established, it then identifies an empty group.

EXAMPLE  An air handler belonging to an air conditioning system is an example of such group assignment.

Figure 3 illustrates an instance diagram.

Figure 3 — Group Assignment

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