Apache Reference: mod_negotiation
mod_negotiation - Content Selection by Best-Matching Client Capabilities
Since Apache 1.0, src/modules/standard/mod_negotiation.c
Robert S. Thau, Roy T. Fielding (1995)
The HTTP protocol provides a flexible content negotiation facility controlled by the
Accept-XXX headers. If Options Multi==Views is active, the mod_negotiation module chooses the best representation of a resource (when a resource is available in several different representations, of course) based on the client-supplied preferences for media type, languages, character set, and encoding. It also implements features intended to provide more intelligent handling of requests for clients that send incomplete negotiation information. The internal algorithms in this module are very complex and partly even heuristic, which makes this module really nontrivial --- both to understand and to use.