All project data sets shall contain a single IfcProject instance indicating overall context and a directory of objects contained within. The context definition may include:
the default units
the geometric representation context for the shape representations
the global positioning of the project coordinate system
the reference to classification systems, or other external information sources, used
the registry of object types and property templates used in the project context
The following diagram shows the generic classes and relationships used when applying this concept.
In addition, concepts may have particular importance to common or standardised industry practices and scenarios. For these specific usage scenarios, the table below shows a recommended list of general usage patterns that users may adopt.