The root element of a Structured Extension construct MAY have attributes, it MAY contain well-formed XML content, or it MAY be empty.
It took me a minute to realize that the content of a structured extension element could be a text node--that it needn't have element children. The name "structured extension" lends itself to this misperception. Perhaps this paragraph could have a sentence or phrase added to it to ensure that that is clear. For example:
The root element of a Structured Extension construct MAY have attributes, it MAY contain well-formed XML content (including unstructured character data), or it MAY be empty.
The presence of an Extension construct MUST NOT redefine the meaning of another Extension construct or core element.
Does this mean that an Extension construct cannot redefine the meaning of another Extension construct from the same namespace, or does it only restrict interaction across namespaces?
The meaning of the namespaced-qualified XML element used as the property name SHOULD be defined by an Atom extension specification, or by a compatible vocabulary.
I'm not sure I have any idea what this means. Does it mean that extensions should have an Atom-specific document describing them? Is there more to it than that?
