(This Recommendation is closely related to Recommendation 2 since HL7 CDA Headers are derived from the RIM and define the semantics of entries in a document)

The RIM methodology consists in defining a set of 'normative' classes (Act, Role, and so on), with which are associated a rich stock of attributes. When the RIM is applied to a new domain (for example pharmacy), one needs to select from just these pre-defined attributes, rather as if one were attempting to create manufacturing software by drawing from a store containing pre-established parts for making every conceivable manufacturable thing, from lawnmowers to hunting bows. We do not know of even one example where a methodology of this sort has been made to work successfully. However, this problem might be overcome if there were a sufficient number of available building blocks to choose from. Thus, there is a need for a lot more pre-defined classes and attributes. The CEN standard on EHR communication (EN 13606), on a side, and the ANSI-HL7 Clinical Document Architecture (CDA), complementary to HL7 v3, allow to manage structured clinical data and their attributes, embedded within clinical documents, on the basis of XML tags.

By defining the structure of a particular clinical document (e.g. the discharge letter) as an XML schema, based e.g. on HL7-CDA, a further degree of semantic interoperability is achieved, providing the documentation background for each data element.

The documentation background is a proxy to preserve some basic attribute and the links among some clinical variables, but it is not possible to predict which variables are actually essential for each particular clinical task (i.e. which clinical data set should be used).

What are called 'Acts' (roughly: intentional actions) play an overwhelmingly central role in the RIM, so that of its 'foundation classes' only Entity (defined as: 'A physical thing, group of physical things or an organization capable of participating in Acts, while in a role') is left over to comprehend those things which are not Acts. How, on this basis, can the RIM deal transparently with information about, say, disease processes, drug interactions, wounds, accidents, bodily organs, and many other phenomena central to healthcare, given that the latter are neither Entities nor Acts? It is beyond the scope of this document to tackle this difficult question. Whatever the solution to this problem may be, the following recommendation can be given on the basis of the current situation.