- From: Mark Nottingham <mnot@mnot.net>
- Date: Thu, 12 Mar 2009 16:02:27 -0700
- To: HTTP Working Group <ietf-http-wg@w3.org>
I compiled this list of notes on the major differences, from the perspective of -05, to help reviewers. Apologies for sending it out late; I've been sick for a few days. 1. Introduction Shortened. 1.1. Purpose "expiration mechanism" -> "freshness mechanism" Small editorial changes (e.g., getting rid of "we") Removed concept of "semantic transparency" 1.2 Terminology Changed definition of "first-hand" Slight disambiguation of "stale" Added definition of "shared cache" 1.3 Requirements No change. 2. Notational Conventions and Generic Grammar Changed to 1.4 Syntax Notation and subsections. 3. Overview Changed to "Cache Operation" Substantially restructured into 2.1 Response Cacheability and 2.2 Constructing Responses from Caches. 3.1 Cache Correctness Removed concept of "cache correctness" Moved requirement related to most recent response to 2.2 Constructing Responses from Caches. Move requirement related to in-transit stale responses to 2.3.3 Serving Stale Responses. 3.2 Warnings Most Warning-related text moved to Warning header definition Downgraded most requirements for sending and displaying Warning to SHOULD 3.3 Cache-control Mechanisms Removed. 3.4 Explicit User Agent Warnings Mostly removed; requirement to display downgraded to a SHOULD; see Warning header definition. 3.5 Exceptions to the Rules and Warnings Moved to 2.3.3 Serving Stale Responses. Requirements here in conflict with those elsewhere. 3.6 Client-Controlled Behaviour Moved to 2.3 Freshness Model; still in progress. 4. Expiration Model Changed to "freshness model" 4.1. Server-Specified Expiration Moved into 4. Expiration Model; substantially reworked. 4.2 Heuristic Expiration Moved to 2.3.1.1 Calculating Heuristic Expiration 4.3 Age Calculations Substantially shorted (probably can be more); now 2.3.2 Calculating Age. 4.4 Expiration Calculations Moved to 2.3.1 Calculating Freshness Lifetime Algorithm re-specified 4.5 Disambiguating Expiration Values Subsumed by other requirement to always use most recent response; see 2.2 Constructing Responses from Cache 4.6 Disambiguation Multiple Responses Subsumed by other requirement to always use most recent response; see 2.2 Constructing Responses from Cache 5. Validation Model See 2.4 Validation Model. Rewritten for clarity. 6. Response Cacheability See 2.1 Response Cacheability 7. Constructing Responses from Caches See below. 7.1 End-to-End and Hop-by-Hop Headers Removed, as it's specific to proxies, not caches. TODO for p1. 7.2 Non-Modifiable Headers Removed, as it's specific to proxies, not caches. TODO for p1. 7.3 Combining Headers See 2.7 Combining Responses. Scope slightly broadened to include non-conditional 206 responses. 8. Caching Negotiated Responses See 2.6 Caching Negotiated Responses. 9. Shared and Non-Shared Caches Moved to 1.2 Terminology 10. Errors or Incomplete Responses Cache Behaviour Split into 2.1.1 Storing Partial and Incomplete Responses, and 2.4 Validation Model 11. Side Effects of GET and HEAD Removed and now in p2-semantics. 12. Invalidations after Updates or Deletions See 2.5 Request Methods that Invalidate 13. Write-Through Mandatory See 2.2 Constructing Responses from Cache Changed from GET and HEAD to unsafe methods. 14. Cache Replacement Subsumed by requirement to use most recent response; see 2.2 Constructing Responses from Cache 15. History Lists See 4. History Lists 16. Header Field Definitions 16.1 Age Minor edits and shuffling from the age calculations section. 16.2 Cache-Control (and subsections to 16.2.5) Flattened organisation to request and response directives. Rewrite directives for clarity. 16.2.6 Cache Control Extensions No substantive changes. 16.3 Expires Cut down duplication with the freshness model section. 16.4 Pragma Removed redundant requirements. Deprecated Pragma. 16.5 Vary Minor rewrite to reduce duplication. 16.6 Warning Major rewrite to reduce duplication. Reduced most requirements to SHOULD. -- Mark Nottingham http://www.mnot.net/
Received on Thursday, 12 March 2009 23:03:06 UTC