Wirtschaftsuniversität Wien Magisterarbeit - SemanticLab

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Listing 3.3: Policy reference file (Source: [W3Ca])
Please note that both P3P policies and policy reference files make extensive use of
wildcards by using the asteriks (“*”). Wildcards can be applied to every URL, for
example to define that policy “fourth” is only applied to JPEG files on the website:
/ ∗ . jpg
Listing 3.4: Policy reference file using wildcards
Both elements INCLUDE and EXCLUDE (and their content, respectively) are casesensitive,
that is, depending on the webserver, one has to make sure that all possible
file-extension combinations are accounted for.
When it comes to third-party content, referencing a policy is not easily accomplished
as URL’s always have to be relative to the policy reference file of the website
and the P3P specification does not allow the application of policies on third-party content.
However, a methodology was introduced to hint user-agents at the policy which
can be applied for third party content by using the HINT element. User-agents should
first check the well-known location of the third-party website for applicable P3P policies.
If no (applicable) policies can be found, user-agents may evaluate the HINT element to
be directed to the third-parties’ P3P policies. However, the HINT element may only be
used if the third-party site declares the location of its policy reference file either via a
HTTP header or LINK tag (because the well-known location was already checked before
the HINT element was evaluated). The HINT element can be used by defining a scope
of the policy and a path relative to the website where the policy reference file is located
as shown in Listing 3.5
Listing 3.5: Policy reference file using the HINT element (Source: [W3Ca])
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