4. Fundamental concepts and assumptions
4.1 Roots
4.1.1 Identity
4.1.2 Revision Control
4.2 Project
4.2.1 Project Declaration
4.2.2 Project Units
4.2.2.1 Conversion Units
4.3 Association
4.3.1 Classification
4.3.2 Constraint
4.3.2.1 External Data Constraints
4.4 Definition
4.4.1 Object Typing
4.4.2 Property Sets
4.4.2.1 Properties for Occurrences
4.4.2.2 Properties for Types
4.4.3 Quantity Sets
4.4.3.1 Quantities on Occurrences
4.5 Assignment
4.5.1 Control Assignment
4.5.2 Group Assignment
4.6 Composition
4.6.1 Aggregation
4.6.1.1 Spatial Composition
4.7 Connectivity
4.7.1 Spatial Structure
4.7.1.1 Spatial Containment
4.7.2 Sequential Connectivity
4.8 Actor
4.8.1 Contact
4.9 Process
4.9.1 Task Scheduling