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RE: Late binding

From: rrw <rrw@semiramis.org.uk>
Date: Thu, 27 Jun 2002 13:07:01 +0100
Message-ID: <15642.65509.66910.916611@haydn.cluster.local>
To: "'w3arch'" <www-ws-arch@w3.org>

On Wednesday 26 June 2002, Martin Chapman
<martin.chapman@oracle.com> wrote:

>
>Couple of points. In other contexts this is the static vs dynamic typing
>debate. Both have merits and have their place.
>
[snip]
>doesn't care. But when bar recieves the get/post it has to decode the
>contents and "route" the request to the implementation of baz, goo, or
>gurgle. If one of these doesn't exist the request fails. All that is
>happening here is that we have pushed the brittleness up one level. You
>*cannot* avoid the problem   that there may be a request for a server
>function/feature/method that does not exist.

 Nor can we fully avoid the problem that you're not really sure what
 the `gurgle' function does. I suspect, however, that sooner or later
 we'll end up with a meta-language describing the important features
 of the semantics of certain requests[1] - in fact, WSDL has it now, in
 the sense that you can document whether you were expecting a reply
 or not.

 So, rather than just `this service has baz, goo and gurgle', you'll
 have a bit more information - `this service is an instance of the
 pattern ModifyableAttribute, and has baz (instance of ReadAttribute),
 goo (instance of WriteAttribute), and gurgle (instance of
 HasSideEffectsOnAttribute). The name of the attribute for `baz' is
 encoded in the parameters `herring' and `wombat'.'.

 Once you have that much information, you can start to use the
 interface (e.g. you can present the user with the ability to control
 it) without really knowing much about what you're controlling[2].
 WSDL will somewhat already do this for you, given a suitable set of
 local naming conventions.

 The interesting question now becomes just how you specify these
 prototypes. The theoreticians would probably use communicating
 automata and type theory, but I suspect the approach that's likely
 to be taken is fairly literal and class-based.

 What it would be nice to see is a hybrid of the two: a class-based
 hybrid somewhat similar to Many-Sorted Polymorphic Typing
 (though I think first-class classes in the type system might be
 a better way of approaching object orientation) would be nice[3].

 Of course, no-one has ever (to my knowledge) tried anything of
 this sort on a wide scale. It works fine for generating
 trivial user interfaces to automatically discovered services, but
 only time will tell how well it scales.


Richard.
[1] <fx: flashback> In much the same way that ML was to be used to
describe the semantics of CPL.
[2] Of course, at least in user-facing terms, this is going to get
 very fuzzy very quickly.
[3] Though note that most type systems that allow quantification and
 implicit typing are going to lead to potential DoS attacks.
Received on Thursday, 27 June 2002 08:07:09 GMT

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