RE: [security-services] Moving subjects up to assertions (disregardfirst reply)

Per the focus call, I'll offer my proposal as an alternative and obviously
encourage others to do so if they don't like Eve's or mine.

Basically I advocate making <Subject> optional in the existing core-07
schema proposal, which has factored it up to <Assertion> level. That is the
extent of my proposal's schema change.

I would then add language to the spec for the existing three statement types
plus any future subject-based statement extensions that basically says
something like:

"An assertion containing such a statement MUST contain a <Subject> element
as defined by sec. XX. If a <Subject> is not provided, then any such
statements are invalid and MUST be ignored. This <Subject> element applies
to all such statements in the assertion. Any other statements MUST define
their relationship to the <Subject> element, if any."

Wordsmithed as need be, but that's the gist.

I would even be fine with adding <SubjectStatement> back in and having it
merely hold SessionIndex, and then derive our statements off it. Then all
the language goes in there, which makes things easier. Not sure if the
notion of session makes sense without a <Subject>, but I doubt it.

-- Scott