office:version (ODF all versions)

Dear all,

ODF documents valid to the ODF schema can use the office:version
attribute to indicate which version of the spec they claim conformance
to.

However, this attribute is optional (something implementations take
advantage of, by sometimes omitting to use it).

When this attribute is absent, how can a document consumer know which
version of the spec is meant to be in force?

I believe this attribute should be mandatory, otherwise meaningful
conformance testing for ODF documents become impossible in cases where
it is not used.

- Alex.