The content in this section is useful and confusing at the same time.

The section is trying to come to a shorthand definition for defining shorthand that stands somewhere in the middle between formal ANTLTR and text. Although I do see the value of the notation in the specification, as it is more accessible than when using ANTLR, it does leave more room for interpretation. It also introduces another layer in which inconsistencies can occur.

Also some of the concepts introduced in this section do not appear in the grammar (e.g. CodeableConcept, datatype) or are using a different name (e.g. decimal vs NUMBER). Sometimes the grammar uses the same keyword for something else (e.g. Resource in this section relates to a resource name, in the grammar it is a resource definition).

Resolving this is tricky, but seeing the importance of this semi-language in the spec, I think this has be done.

One approach could be to separate the notational elements from the definitions and list or refer to the exact definitions for those elements that relate to the formal language specification; expressing each syntax term in ANTLR using the formal ANTLR definition.