[security-services] Text for Spec: SAML Philosophy

[Hal Lockhart <hal.lockhart@entegrity.com>]

Title: Text for Spec: SAML Philosophy

Proposed text for the introduction.

The general philosophy behind the SAML specifications can be briefly summarized in this way.

o   Asserting Parties speak the truth as far as they know it.
o   Relying Parties use the information however they choose.

This has a number of implications, including:

1. The meaning of a SAML Assertion depends only on its contents and not the means by which it was obtained, except for the determination of the Subject to whom it refers. For example, receiving the same Assertion several times does not alter its meaning.

2. A Relying Party makes its own decision about how to validate an assertion and what information to rely on under what circumstances. For example, a Relying Party may trust some portions of an assertion from one Asserting Party and other portions from another. It is up to the Relying Party to make its own determination as to how recent an assertion must be and the means whether the means of insuring its integrity are sufficient.

Application of these principals will provide guidance to implementers in cases where the specification is silent or ambiguous.

Hal