The objectified relationship IfcRelAssignsToGroupByFactor is a specialization of the general grouping mechanism. It allows to add a factor to define the ratio that applies to the assignment of object definitions (individual object occurrences as subtypes of IfcObject and object types as subtypes of IfcTypeObject) to a group (subtypes of IfcGroup). The ratio can be used to define a percentage assignment. For example, a Factor of 0.8 would indicate that the object is assigned by 80% to the group, or a Factor of 2.5 would indicate the object is assigned with a weight factor of 2.5 to the group. 

The same object or object type may be included with the same or different Factor values to many groups. Grouping relationships are not hierarchical.

Examples of factored groups include the assignment of load cases in a load combination in structural analysis, or the assignment of spaces by percentage to different rental zones.