Working towards the next version of the SWIM Supporting Material
The specification requires only a minimum amount of details for the concepts. This reflects the focus on semantic interoperability. However, more details such as multiplicity and data value ranges can be added to the information definition. Indeed, the Specification for Service Descriptions, SWIM-SERV-022 requires more.
The note to the requirement in the Specification mentions that is possible to include "more details such as the relationships between concepts". This is often done by adding associations in UML models, or by using attributes to link different concepts. The Specification does not recommend one technique over the other. Indeed, the Specification does not mention techniques at all as the manner of adding relationships differs depending on the format used for the information definition.