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Subject: RE: [wsrp-wsia] [I#97] Caching Mechanism


Good point.
 
OK, so I'll change the proposition so that expires is an integer defining expiration time (in seconds). Anybody opposing that?
 
Gil
-----Original Message-----
From: Sasha Aickin [mailto:AlexanderA@plumtree.com]
Sent: Tue, September 24, 2002 02:59
To: Michael Freedman; wsrp-wsia@lists.oasis-open.org
Subject: RE: [wsrp-wsia] [I#97] Caching Mechanism

I believe that HTTP switched to using an integer based expiry (i.e. max-age) mechanism (rather than date) to get around the problem of unsynchronized clocks.  If you send an absolute time (in an absolute time zone), you are depending on the clocks on the client and server being in sync.  A lot of applications want to cache content for just a few minutes, which is well within the possible error of clock synchronicity.
 
If for some reason we really want to use an absolute date for expiry, the server would have to send back its current date so that the client can calculate how long the content should remain fresh.  We would also have to be explicit that the expiry date was to be calculated relative to the server's returned current date.
 
Cheers,
Sasha.
-----Original Message-----
From: Michael Freedman [mailto:Michael.Freedman@oracle.com]
Sent: Monday, September 23, 2002 4:51 PM
To: wsrp-wsia@lists.oasis-open.org
Subject: Re: [wsrp-wsia] [I#97] Caching Mechanism

If I recall correctly, "expires" refers to the refHandle not the content.  I.e. it defines the length of time the refHandle will be valid for between requests.  As such it is a duration -- which is reset per request.  Hence its definition as an "int".  Content expiration isn't affected by access, hence using an absolute time can be considered.  Using a duration, however, would also be valid.  We need to decide which is more common/convenient for our developers.  I.e. Is it more common/easier to say this content expires in 30 minutes or to dynamically compute when 30 minutes from now is (in some absolute timezone form)?
     -Mike-

"Tamari, Yossi" wrote:

 Hi Gil,I must be misreading the spec, because it seems to me that expires is an int number of seconds currently in the spec (which may not be the the right way, but that's what was decided).As for scoping to the Producer, can you please explain how that works around the need for other scopes (unless they are coded into the validationTag)?    Yossi.
-----Original Message-----
From: Gil Tayar [mailto:Gil.Tayar@webcollage.com]
Sent: Monday, September 23, 2002 7:23 AM
To: wsrp-wsia@lists.oasis-open.org
Subject: RE: [wsrp-wsia] [I#97] Caching Mechanism
 
Good questions.On the scope question, I would scope it to the Producer. This is the easiest and works around problems with the other scopes.On the type of time - the validUntil is a "date-time" field just like Expires is, and I suggest we use the xsd:dateTime type for it (or whatever its exact name is). This means that the time is an absolute time.
-----Original Message-----
From: Tamari, Yossi [mailto:yossi.tamari@sap.com]
Sent: Thu, September 19, 2002 17:56
To: 'Gil Tayar'; wsrp-wsia@lists.oasis-open.org
Subject: RE: [wsrp-wsia] [I#97] Caching Mechanism
 
What is the scope of the cached fragments? user? session? entity? Should this be explicitly returned in the markupResponse or in the metadata of the entity, or does the entity encode it into the validationTag if it wants to?Should we return the (absolute) expiration time or the (relative) amount of time until expiration? on the "expires" field I was for expiration time but I was out-voted.    Yossi.
-----Original Message-----
From: Gil Tayar [mailto:Gil.Tayar@webcollage.com]
Sent: Thursday, September 19, 2002 9:03 AM
To: wsrp-wsia@lists.oasis-open.org
Subject: [wsrp-wsia] [I#97] Caching Mechanism
 
Topic: interfaceClass: TechnicalTitle: Caching MechanismDocument Section: Interfaces/6.1Description:I am submitting the following proposition to the committee as a proposition for dealing with caching of the markup. This proposition deals with "Expires"-like methods of caching, along with "If-Modified-Since/ETags" type of caching. I believe it is simple enough to be included in the v1.0 spec.Caching Proposal[The proposal is described as edits to the spec]6.1 Operations [getMarkup][instead of expires in markupResponse, add the following]cacheControl: A data structure, defined in Section 11, which includes information which CAN be used by the Consumer to cache the markup. This structure includes:    validUntil: The time at which the markup is valid. Until that time the Consumer CAN use its cache entry instead of calling getMarkup. After this time passes, the Consumer MAY continue to use this cache entry, but only after validating it with a getMarkup operation, using the validationTag below, if given.    validationTag: The Consumer MUST store this tag along with the markup while the markup is valid. This enables the Producer to use this tag to invalidate the cache entry by sending an invalidationTagPrefix in the performInteraction operation. After the markup expires, the Consumer CAN send the validationTag in the markupResponse to indicate that it still has the markup but would like to validate it. The Producer returns a fault response [TBD] to indicate that the markup is still valid, otherwise if it returns markup , the Consumer MUST invalidate the old markup.[add to markupContext the following field]   validationTag: This field CAN be sent to indicate that the Consumer has cached markup (which was tagged by the Producer with this value) and wishes to check whether it is still valid. See validationTag in markupResponse for more information. 6.1 Operations [performInteraction][add the following field to interactionResponse]    invalidationTagPrefix: If the Producer returned this value, the Consumer MUST expire all markup-s who's validationTag begins with this value. The Consumer MUST not call getMarkup with these invalidationTag-s to validate these expired markup-s. [add these fields to the relevant places in section 11]%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Discussion:


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