Glossary issue with the term "Principal"

[Rainer Hoerbe <rainer@hoerbe.at>]

As I do not yet have a privilege to create issues in JIRA, I am sending this issue to the list.

SAML Glossay 2.0 defines the term Principal as "A system entity whose identity can be authenticated. [X.811]". Other definitions, however, contradict this in other definitions by using "principal" implicitly for non-system entities (aka. users), as in Account, Affiliation, IDP, Persistent Pseudonym, etc.
In addition this is not a correct citation of X.811, which says "An entity whose identity can be authenticated."

I suggest to fix this in 2.1 by clarifying the definition, e.g. with this wording:
"An entity whose identity can be authenticated and which can be the subject of a SAML assertion"

My rationale to raise this issue was, that an "UnknownPrincipal" exception should have revealed without using a debugger that the cause was a metadata misconfiguration, not a problem with the user's login account.

- Rainer