saml assertion schema notes

[Simon Godik <sgodik@crosslogix.com>]

Title: saml assertion schema notes

notes on draft-sstc-core-discussion-00.doc

Assertion type has 4 required attributes. Also we have to specify
xsi:type for each assertion instance. It will make 5 required attributes
for each assertion. I think it will be difficult to read. Why not make
4 required attributes in base assertion into elements and have one xsi:type
attribute?

Advice element could be misused for anything that does not fit into
assertion.

There are many abstract types but only AbstractConditionType has 'Abstract'
in it's name.  It is confusing: we either should use 'Abstract' in the name
of every abstract type or not at all.

There is a typo on line 249 for the SubjectType: Authenticator is referenced
but everywhere in the text HolderOfKey is mentioned. I belive there is still
an open issue on this element name.

It is not clear what can be a subject of AuthenticationAssertion.
Definetely AssertionSpecifier should not be used in this case but schema
does not preclude it. (AssertionSpecifier will give us self-reference and
subject will be left undefined)

Simon Godik