Profiles should combine several ConformanceUnits. It is recommended, that concrete domain-specific Companion Specifications define at least one application profile (defining everything that is needed for a product including protocol etc.) to improve interoperability in that domain.

Generic Companion Specifications designed to be used by others may only define Facets or even only ConformanceUnits which then may be used by other Companion Specifications. If a group of functionalities is expected to be added into other specification it is recommended that that group be defined in a Facet, which can make it much easier to reuse a model. These Facets can be used in an overall Profile that is defined in a Companion Specification.