Existing Wording: All resources have the following optional or mandatory elements and properties: an identity, meta data, a base language, a reference to "implicit rules"

Proposed Wording: All resources may contain the following elements and properties: an identity, meta data, a base language, a reference to "implicit rules" If contained in a resource, the elements may be mandatory or optional.

Comment:

This is confusing as worded and doesn't seem consistent with the resource definitions that I see. For example, if "all" resources have these elements, why don't I see them all in every resource? E.g., the Patient resource spec (5.1.x) doesn't list id, meta, base language, or implicit rules, although id is shown in some of the Examples.

When 1.10.2. says "optional or mandatory" I'm not sure whether by "optional" it means that "the element is present with cardinality 0..1 or 0..*," or whether it means that "the element may be absent." IF it means the element may be absent, then the alternative wording may be clearer.