- From: Roy T. Fielding <fielding@gbiv.com>
- Date: Tue, 31 Mar 2009 19:44:57 -0700
- To: HTTP Working Group <ietf-http-wg@w3.org>
It is impossible to determine a media-type (how a recipient should process a given representation) by sniffing the content (the data format). Many media-types overlap the same data formats. Many media types are only distinguished from other types by what the user agent should do when processing them, not by the bits on the wire. When a media type is not present (or is detectably incorrect), only the implementation doing the processing can determine an appropriate guess because that guess is almost always determined by the context in which the reference was made (not by the content). Since the context is deliberately not sent on the wire, there is absolutely no way that accurate sniffing can be defined by HTTP. We aren't talking about a protocol decision regarding communication; we are talking about an operating default that is specific to the purpose of a given client and will likely be different for each one. In any case, there is no algorithm for sniffing that is anywhere near the same level of standardization as HTTP. The one that HTML5 is working on would barely qualify as Experimental. If the folks promoting such software can successfully deploy it across all HTTP clients, then it should be referenced. Until then, it remains an unproven and, IMO, mistaken idea which is far more likely to be overcome by events than become a standard way to handle HTTP. ....Roy
Received on Wednesday, 1 April 2009 02:45:35 UTC