Composition is used for various 'organizer' purposes. While for some uses, these elements are indeed mandatory, for other uses they're not necessary - e.g. defining the hierarchy of artifacts in an ImplementationGuide. Composition is not only about documents - it's an "organizer of data". Elements are only allowed to be mandatory if they are truly necessary to the use of the resource across all use-cases. (The fact that someone can 'make something up' to satisfy the mandatory isn't acceptable. Implementers should NEVER have to populate elements that have no value. You can always define a 'FHIR document' profile and make these elements mandatory there.)

(Comment 95 - imported by: Ron G. Parker)