Identifier at the source system for the instance-variable. Used during import to determine if the entity already exists in the target system (update) or is new (create). Must remain stable in the source system for the same entity. The designation of the instance variable Explanation of the instance variable The operational definition of the variable in context, describing how it is concretely measured or observed. Corresponds to the GSIM Concept. Reference to Population (observes population) Reference to RepresentedVariable (uses representation) Reference to Dataset (belongs to dataset)