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The IdP has built-in support for processing tags, and where possible automatically decoding and caching them in hashtables for ease of lookup. These data structures are complex but the predicate class handles that automatically and knows how to check for both the decoded (“mapped”) tags as well as (if desired) to actually search through the underlying metadata objects for unmapped tags in unusual cases.
There is a second variant called shibboleth.Conditions.EntityAttribute that searches the underlying metadata objects instead of the decoded, cached tag data. This is less efficient but has the advantage that the tags do not need to be decoded to find them. This is mostly useful because tags that do not carry the URI NameFormat will not be automatically decoded without dedicated transcoding rules defined in the registry, so if you don’t want to define the rules or use URI naming, this is an alternative.
Overview
Tags are an informal term for the attaching of <saml:Attribute> elements into a piece of metadata using a standard extension. Tags can express general, unconstrained information about an entity without having to define XML schema extensions specifically for every possible piece of information one wants to express.
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