This Wiki page is edited by participants of the Protocols and Formats Working Group. It does not necessarily represent consensus and it may have incorrect information or information that is not supported by other Working Group participants, WAI, or W3C. It may also have some very useful information.
Notes on HTTP
PFWG noted a concern about Cache-Control: no-transform during a review of Guidelines for Web Content Transformation Proxies. This turns out to be a feature of the HTTP specification that WCTP just mirrored. PFWG discussion of Cache-Control: no-transform identified some problems for accessibility with this feature, and acknowledged cases where it needed to be respected in spite of accessibility concerns.
Problems for accessibility:
- Accessibility transcoding tools core functionality is to do a transformation and need right to do so.
- Example of transforming star positions into sound - it was a clear situation when the data needed to be transformed.
Reasons Cache-Control: no-transform must be respected:
- There are things like medical data that needs to be sent end to end with no changes.
- There are lots of situations where you are accessing via proxies and there is no alternative. You need to have a way to ensure that the data is not being transformed.