- From: Roy T. Fielding <fielding@avron.ICS.UCI.EDU>
- Date: Tue, 16 Apr 1996 14:43:10 -0700
- To: Jeffrey Mogul <mogul@pa.dec.com>
- Cc: http-caching@pa.dec.com
>>> The change-indicator is used to indicate changes to the content of
>>> the resource uniquely identified by the Request-URI and variant-id.
>>> The change-indicator value SHOULD change when the content of an entity
>>> changes and SHOULD NOT change when the content remains the same.
>>> When the value changes, it MUST change to a value not already used for
>>> that entity within a timeframe for which there may still exist
>>> legitimately cached entities with the same change-indicator value.
>> ...
>
> At any rate, my compromise solution to this argument is to
> say nothing about it in the spec. That is, the specification
> now says:
> In order to be legal, a strong opaque validator MUST change
> whenever the associated entity value changes in any way. A weak
> opaque validator SHOULD change whenever the associated entity value
> changes in a semantically significant way.
> and says nothing about when the values can be reused or not. Maybe
> we should include some "advice to implementors" about this later on.
That's too weak -- we definitely don't want people implementing just
a toggle and claiming compliance. How about
When the value changes, it SHOULD change to a value not already used for
that entity within a reasonable timeframe for which there is likely
to exist legitimately cached entities with the same change-indicator
value.
Vague, yes, but at least it makes the point.
.....Roy
Received on Tuesday, 16 April 1996 22:35:33 UTC