The PPID claim enables you to de?¬?ne a unique, site-speci?¬?c
value that you can pass to the RP so that the RP can recognize the same user returning
each time, regardless of the uniqueness of other claims.
338 Identity Providers
Reliability
When users and RPs begin to rely upon the presence of
Information Cards, it is critical that access to them remain
available. Whereas a user blocked temporarily
from accessing a service due to a failed STS would impair
business continuity, a whole organization knocked
of?¬‚ine because of the same problem could be a disaster.
Walking a Mile in the User??™s Shoes
When the IP chooses what claims are present in a card, each of
the claims in the token would ideally present a logical piece of
data to which the user can relate. Because the IP dictates the
format of the token (or adopts a format supported by the industry),
it is possible that the data in the claims is somewhat obfuscated
or collated into a few big claims stored in binary large
objects (BLOBs) or Extensible Markup Language (XML)
fragments. To ensure that the users are given the opportunity to
inspect the value of the claims asserted about them in a meaningful
way, CardSpace includes a display token??”a copy of the
claims in the token to be expressed in a way that is readable to
the user.
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