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The Conformance section of the Guidelines for Web Content Transformation Proxies specification requires Transformation Deployments that wish to claim conformance to the specification to make available a conformance statement that specifies the reasons for non-compliance with any clauses containing the key words should or should not. This presentation is intended to provide a base template for such a conformance statement.
The table includes spaces for scoring each statement: "Compliance" to assert compliance and "Reason for non-compliance" to specify the reasons for non-compliance with a given clause. Non-compliance to absolute requirements of the specification, i.e. normative statements that use the terms must, must not, shall or shall not, is forbidden. The "Reason for non-compliance" column of absolute requirements is marked as "N/A" (Not Applicable).
Proxies should not intervene in methods other than GET, POST, HEAD.
If the HTTP method is altered from HEAD to GET, proxies
should (providing such action is in accordance with
normal HTTP caching rules) cache the response so that a second GET request
for the same content is not required (see also 4.1.4 Serving Cached Responses ).
[...] In this case proxies may
for the sake of consistency of representation serve stale data but when
doing so should notify the user that this is the case [...]
Aside from the usual procedures defined in [RFC 2616 HTTP] proxies should not modify the values of header fields other than
the User-Agent, Accept, Accept-Charset, Accept-Encoding, and Accept-Language header fields [...]
Other than to comply with transparent HTTP operation, proxies should not modify any request header fields unless: [...]
[...] Since the concept of "Web site" is not strictly defined, proxies should use heuristics including comparisons of domain name to assess whether resources form part of the same "Web site".
[...] g. style sheets, images), proxies should
make the request for such resources with the same User-Agent header field as the request for the resource from which they are referenced.
When requesting linked resources that do not form part of the same Web
site as the resource from which they are linked, proxies should
not base their choice of header fields on a consistency of presentation premise.
[...] and should indicate their ability to transform content by including a comment in the Via HTTP header field consisting of the URI "http://www.w3.org/ns/ct".
When forwarding Via header fields, proxies should
not alter them by removing comments from them.
[...] However, if it makes a request with altered header fields in these circumstances, and receives a response containing a Vary header field referring to one of the altered
header fields then it should request the resource again with unaltered header fields.
[...] It should also update whatever heuristics it uses so that unaltered header fields are presented first in subsequent requests for this resource.
If the response is an HTML response and it contains a <link
rel="alternate" media="handheld" /> element, a proxy
should request and process the referenced resource,
unless the resource referenced is the current resource as determined by the
presence of link elements.
In the absence of a Vary or no-transform directive
(or a meta HTTP-Equiv element containing Cache-Control:
no-transform) proxies should not transform content matching the following rules unless the user has specifically requested transformation: [...]
The altered content should validate according to an appropriate published formal grammar [...]
It should indicate to the user that the content has been transformed for mobile presentation and provide an option to view the original, unmodified content.