- From: Larry Masinter <masinter@parc.xerox.com>
- Date: Fri, 14 Jun 1996 09:22:54 PDT
- To: dmk@allegra.att.com
- Cc: dan@spyglass.com, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Re: "if-modified-since: tuesday, 24-Jan-95 00:24:37 GMT; length=116" appearing to be dropped: This was not a case of something "falling off the map", it was an explicit choice to support entity tags instead. A server is free to implement a kind of entity tag which contains both modify date and length. A cache can then just do "if-none-match" on the entity tag, without knowing that the validator included the length. If you want to build a _reliable_ web server for a file system that allows random access to the files and also allows users to modify the write dates, you should chose something other than date & length as the cache validator. On the other hand, date is convenient, and date+length a little more reliable, so some servers will choose to do that. By making the cache validator opaque (rather than explicitly calling out date and length), we could allow many different kinds of validators. Because entity tags are used not only for cache validation but also fresh variant selection, we wanted another name than "cache validator", thus "entity tag". Larry
Received on Friday, 14 June 1996 09:29:44 UTC