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RE: ACTION-58 Look into issues surrounding the use of the 'any' type in the IDL

From: Jo Rabin <jrabin@mtld.mobi>
Date: Tue, 28 Aug 2007 08:58:34 +0100
Message-ID: <C8FFD98530207F40BD8D2CAD608B50B4600404@mtldsvr01.DotMobi.local>
To: "Rhys Lewis" <rhys@volantis.com>, <public-ddwg@w3.org>

As ever, Rhys, it looks as though we substantially agree.

I think we could look more closely at the persistence question. I'm not sure of how much of a burden it is to insist on a restful implementation, even in the presence of dynamically computed keys. The key must be persistent for _some_ period in the context of a session, and presumably during the session the data can be updated and so an implementation needs to find a way of allocating a key at the start of a session and make it stick for the duration. I suppose that a session can be arbitrarily long so how is that different from having a 'persistent' key?

I'd rather avoid defining sessions, especially as some implementations will not require it.

Jo


> -----Original Message-----
> From: Rhys Lewis [mailto:rhys@volantis.com]
> Sent: 28 August 2007 08:32
> To: Jo Rabin; public-ddwg@w3.org
> Subject: RE: ACTION-58 Look into issues surrounding the use of the 'any'
> type in the IDL
> 
> Hello Jo,
> 
> I think we are saying the same thing.
> 
> By the way, I don't think I did say what you thought I said in d). A key
> identifies a context, but doesn't encode it. In other words, I can't take
> a context and peer inside it to get useful information. What I can do is
> hand it back to the DDR implementation and ask it to peer inside for me.
> That's all I meant when I said that users of the DDR can't infer anything
> about the key. It's like a URI. I can use it to uniquely identify a
> context, but I can't tell anything about the context from the key itself.
> I can however hand the key to an API that can tell me about the context.
> 
> On scope, I don't think keys can have global scope. Data in a DDR changes
> over time and that could affect the computation of a key. Computing the
> key on every access is potentially very expensive. Sessions provide a nice
> compromise. It's a purely practical issue.
> 
> Best wishes
> Rhys
> 
> 
> -----Original Message-----
> From: public-ddwg-request@w3.org [mailto:public-ddwg-request@w3.org] On
> Behalf Of Jo Rabin
> Sent: 28 August 2007 08:20
> To: public-ddwg@w3.org
> Subject: RE: ACTION-58 Look into issues surrounding the use of the 'any'
> type in the IDL
> 
> 
> 
> My 2 Euro Cents on this as follows:
> 
> a) I think the context key needs to be of a known standard type between
> implementations - I am not sure I am happy with an integer, I'd be happier
> with a string which allows more flexibility. That said, I'd be equally
> happy with any other arbitrary length structure or happier still with an
> opaque Object.
> b) I don't think an instance of a context key is portable between
> implementation types
> c) it may be portable between instances of the same type - that's up to
> the implementation
> d) I'm not sure I understand when Rhys says that a context key doesn't
> identify a context, because inter alia it seems to me that it does
> identify aspects of a context but only to instances as discussed above
> e) I am having difficulty with how persistent a context key needs to be.
> When discussed in the context of a 'session', I find this difficult to
> reconcile with the idea of the API being implemented in a RESTful way.
> 
> Jo
> 
> 
> > -----Original Message-----
> > From: public-ddwg-request@w3.org [mailto:public-ddwg-request@w3.org]
> > On Behalf Of Rhys Lewis
> > Sent: 28 August 2007 08:00
> > To: 'Matt Womer'
> > Cc: 'Josť Manuel Cantera Fonseca'; public-ddwg@w3.org
> > Subject: RE: ACTION-58 Look into issues surrounding the use of the 'any'
> > type in the IDL
> >
> >
> > Hi Matt,
> >
> > Yes, I think the key has to be completely opaque.
> >
> > I'm not sure I get the distinction between using some type of hash on
> > an instance of a context and an  integer. As long as the user of the
> > key can't tell what's inside it, without asking the implementation of
> > the DDR, it doesn't really matter. Integers are just easier to hand
> > around and are of predefined length.
> >
> > So, I think we are both saying the following:
> >
> > - The context is an implementation-specific data structure that is
> > internal to the DDR implementation
> > - The context key is an opaque way for a user of the DDR to refer to a
> > particular context
> > - Users of a DDR get a context key in response to specific operations.
> > These include DDR operations to
> >   identify a context from a set of HTTP headers, for example.
> > - Users of the DDR can ask questions about the context. In doing so,
> > they supply the appropriate context
> >   key to the appropriate DDR API.
> > - Users of the DDR cannot infer anything about the context directly
> > from the value of the context key
> >   itself. In particular, the key does NOT encode the context.
> > - Context keys are NOT portable across different implementations of
> > DDRs
> >
> > Whether the key is an integer or a hash of some kind doesn't really
> > matter. I think in practice that integers would be simpler, but that's
> > just an implementation detail.
> >
> > Does that help?
> >
> > Best wishes
> > Rhys
> >
> >
> >
> > -----Original Message-----
> > From: Matt Womer [mailto:mdw@w3.org]
> > Sent: 27 August 2007 17:47
> > To: Rhys Lewis
> > Cc: 'Josť Manuel Cantera Fonseca'; public-ddwg@w3.org
> > Subject: Re: ACTION-58 Look into issues surrounding the use of the 'any'
> > type in the IDL
> >
> > Hi Rhys, Josť, DDers,
> >
> > On Aug 1, 2007, at 3:32 AM, Rhys Lewis wrote:
> > > If all that sounds correct, then the 'handle' for the context key
> > > merely has to identify it within a session that a caller has with
> > > the DDR.
> > > So,
> > > can't it just be an integer?
> >
> > Thanks for writing this up, it helped me understand where the
> > confusion is coming from.
> >
> > I think of the Context Key IS the opaque handle itself.  It is a
> > handle to the "Context", which is an implementation specific structure
> > in and of itself.
> >
> > I assumed that from the name that it was a 'key' in a list/hash/map of
> > contexts, and I think from your email that this isn't what you're
> > thinking.  RIght?
> >
> > What do other folks think?
> >
> > -Matt Womer
> >
> > mdw@w3.org
> > W3C Team -- http://www.w3.org/
> > Mobile Web Initiative Lead Americas
> > Team Contact: MWI DDWG, POWDER, Voice Browser
> >
> >
> >
> 
> 
Received on Tuesday, 28 August 2007 07:58:48 UTC

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