Reference Models form part of the Production Environment (PE) infrastructure and serve to formalise the construction and interpretation of Domain Models (defined in the Technical Model Artefacts package) by defining the basic structures, semantics and constraints to which Domain Models must conform. The LRA defines Data Types, Care Components and Participants Reference Models. In addition the Data Types and Care Components Reference Models are derived by constraint from the imported Reference Models ISO 21090 and EN 13606-1 respectively.