Editing Industry Foundation Classes (section)

===IfcObjectDefinition===
IfcObjectDefinition is split into object occurrences and object types.  IfcObject captures object occurrences such as a product installation having serial number and physical placement.  IfcTypeObject captures type definitions (or templates) such as a product type having a particular model number and common shape.  Occurrences and types are further subdivided into six fundamental concepts: actors ("who"), controls ("why"), groups ("what"), products ("where"), processes ("when"), and resources ("how").  
* IfcActor represents people or organizations.  
* IfcControl represents rules controlling time, cost, or scope such as work orders.
* IfcGroup represents collections of objects for particular purpose such as electrical circuits.  
* IfcProduct represents occurrences in space such as physical building elements and spatial locations.  
* IfcProcess represents occurrences in time such as tasks, events, and procedures.  
* IfcResource represents usage of something with limited availability such as materials, labor, and equipment.