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RE: Issue 6413 - just thinking

From: Geoff Bullen <Geoff.Bullen@microsoft.com>
Date: Wed, 6 May 2009 17:45:17 -0700
To: Gilbert Pilz <gilbert.pilz@oracle.com>
CC: "ashok.malhotra@oracle.com" <ashok.malhotra@oracle.com>, Katy Warr <katy_warr@uk.ibm.com>, Yves Lafon <ylafon@w3.org>, Doug Davis <dug@us.ibm.com>, "public-ws-resource-access@w3.org" <public-ws-resource-access@w3.org>
Message-ID: <5AAAA6322448AA41840FC4563A30D6E843A081C70D@NA-EXMSG-C122.redmond.corp.microsoft.com>
Gil,

> Why wouldn't these sub-event sources have their own EPRs?

That is a really good question!  And if sub-event sources should have their own EPRs, then it also makes sense that sub-transfer resources should also have their own EPRs, for the same reason.  However, Doug , on another thread (see http://lists.w3.org/Archives/Public/public-ws-resource-access/2009May/0052.html) has just said:

Once the client has an EPR to a resource, it's just a resource.  The question is, how do you get more granularity if the service won't give you an EPR to something lower down?  ta da... fragments  ;-)

So, based on Doug's comment above, Doug's answer to your question ("Why wouldn't these sub-event sources have their own EPRs?) is that the EPR/Service (M) "won't give you an EPR to something lower down", so therefore you need fragments.

The point that you make Gil, is that the Eventing use case is not valid if fragment access itself is not valid.
But, if fragment access is valid, as Doug contends, then the Eventing use case is also valid.
If the Eventing use case is valid, then the fragment access spec must be separated from the Transfer spec, since the fragment access spec has generic use cases.

--Geoff


From: Gilbert Pilz [mailto:gilbert.pilz@oracle.com]
Sent: Wednesday, May 06, 2009 3:26 PM
To: Geoff Bullen
Cc: ashok.malhotra@oracle.com; Katy Warr; Yves Lafon; Doug Davis; public-ws-resource-access@w3.org
Subject: Re: Issue 6413 - just thinking

Geoff,

I'm missing something here. Why wouldn't these sub-event sources have their own EPRs?

- gp

Geoff Bullen wrote:

Events cannot be broken into fragments.



Possibly not, but event sources certainly can be.



In the same way that one might have an EPR (M) and want to "Transfer/Put" some new content into a fragment (hardware) associated with that EPR, one might also have the same EPR (M) and want to only be sent events generated by a particular fragment (hardware) of the EPR.





-----Original Message-----

From: ashok malhotra [mailto:ashok.malhotra@oracle.com]

Sent: Wednesday, May 06, 2009 2:14 PM

To: Geoff Bullen

Cc: Katy Warr; Yves Lafon; Doug Davis; public-ws-resource-access@w3.org<mailto:public-ws-resource-access@w3.org>

Subject: Re: Issue 6413 - just thinking



I'm sorry Geoff, your analogy from events to a machine with several

parts is not convincing.

Events cannot be broken into fragments.

All the best, Ashok





Geoff Bullen wrote:



Hi Katy,





In theory, I could imagine this might be a possibility but, in



practice, I can't think of a real example. I'm concerned that we'd

create an extra specification that would never be used outside the

context of WS-T.



Many people appear to be saying that because they cannot think of a

real example, therefore none exists, so therefore the WG should not be

taking the fact that an example might exist into consideration. While

this "ostrich" thinking seems rather odd, especially when making such

a fundamental decision concerning a specification, let's look at a

real example:



Consider filtering in Eventing (the same reasoning would also work for

Enumeration).



In the example, we have an endpoint that represents a machine (M).



We want to subscribe to events from M - but not all of them. How do we

do that?



The basic filtering mechanism in Eventing supports an XPath filter

that will allow subscribers to define a subset of the events from M,

based on the content of the event.



Now consider that M has many sub-resources (fragments). For example,

it has an operating system, it has hardware - which, in turn, is made

up of a disk, a CPU, etc. If M had a new filter type that composed

with fragment access, subscribers would now be able to filter the

events not only on the content of the event, but also on the

sub-resource (fragment) that generated the event (i.e. only be sent

events that were hardware related, for example). This would be a very

useful filter in many situations.



Basically anywhere there is a need to provide a filtering mechanism

there is also a potential need to compose with fragment access.





Worse still, a high proportion of use cases will require both specs



so ultimately they will be read as a single specification.



Does this really mean ". a high proportion of IBM use cases ."? The

industry at large has many implementations of Transfer as it stands,

and there are also many other specifications that reference Transfer,

so there appears no real justification for saying that, in general, a

high proportion of use cases require fragment support - it just is not

the case.



--Geoff



*From:* public-ws-resource-access-request@w3.org<mailto:public-ws-resource-access-request@w3.org>

[mailto:public-ws-resource-access-request@w3.org] *On Behalf Of *Katy Warr

*Sent:* Wednesday, May 06, 2009 2:52 AM

*To:* Yves Lafon

*Cc:* Doug Davis; Geoff Bullen; public-ws-resource-access@w3.org<mailto:public-ws-resource-access@w3.org>

*Subject:* Re: Issue 6413 - just thinking





Yves



I guess that by 'more general' you mean that a separate fragment spec

would be re-usable outside the context of WS-Transfer? In theory, I

could imagine this might be a possibility but, in practice, I can't

think of a real example. I'm concerned that we'd create an extra

specification that would never be used outside the context of WS-T.

Worse still, a high proportion of use cases will require both specs so

ultimately they will be read as a single specification.



That said, I fully understand the argument to keep the WS-T

specification 'pure' for scenarios that don't implement fragments. By

placing the fragment text in the appendix (rather than the main body),

we'll do exactly that.



Best regards

Katy



From:







Yves Lafon <ylafon@w3.org><mailto:ylafon@w3.org>



To:







Doug Davis <dug@us.ibm.com><mailto:dug@us.ibm.com>



Cc:







Geoff Bullen <Geoff.Bullen@microsoft.com><mailto:Geoff.Bullen@microsoft.com>,

"public-ws-resource-access@w3.org"<mailto:public-ws-resource-access@w3.org> <public-ws-resource-access@w3.org><mailto:public-ws-resource-access@w3.org>,

public-ws-resource-access-request@w3.org<mailto:public-ws-resource-access-request@w3.org>



Date:







06/05/2009 08:52



Subject:







Re: Issue 6413 - just thinking



------------------------------------------------------------------------









On Tue, 5 May 2009, Doug Davis wrote:





Geoff,

Allow me to turn it around for a sec... if the general premise of

"strongly encouraging" is agreed to, and people do not "want a

proliferation of fragment specs", then an obvious question (to me anyway)

is: what's so bad about having it in Transfer? I've heard (and understand



If the fragment definition is in Transfer, then it is quite likely

somebody else will define another "fragment spec" be it more general, or

attached to another spec. That's why having a standalone document for

fragment definition makes far more sense, it can be referred from

Transfer, but also from other specs that don't want to reuse Transfer.



As I said during the call, fragments definition are more linked to the

addressing or resources than the action on them (and for the record,

having the action distinct form the URI of the service is, well,

suboptimal. At least transfer allows action to be a set of properties,

but

I digress ;) ).



--

Baroula que barouleras, au tiéu toujou t'entourneras.



~~Yves













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Received on Thursday, 7 May 2009 00:46:14 GMT

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