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

From: Rhys Lewis <rhys@volantis.com>
Date: Tue, 28 Aug 2007 00:32:25 -0700 (PDT)
To: "'Jo Rabin'" <jrabin@mtld.mobi>, <public-ddwg@w3.org>
Message-ID: <008801c7e945$eda55880$0202fea9@volantisuk>

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

-----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.


> -----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 07:32:43 UTC

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