W3C home > Mailing lists > Public > www-ws-arch@w3.org > May 2003

Re: REST, uniformity and semantics

From: Walden Mathews <waldenm@optonline.net>
Date: Tue, 13 May 2003 14:13:55 -0400
To: Francis McCabe <fgm@fla.fujitsu.com>
Cc: www-ws-arch@w3.org
Message-id: <003d01c3197b$6b71d580$1702a8c0@WorkGroup>

> You must distinguish the abstract characteristics of description from 
> concrete specifications. I would argue that CORBA gives a similar kind 
> of descriptive power, at this level of abstraction, to SOAP/WSDL. (This 
> is not intended as a comparison, nor as an "I'm better than you" fight.)

I can distinguish that a description of something is abstract from
the thing itself.  Beyond that, you've lost me.  What's a "concrete
specification"?

And back to the subject of services and meanings, saying that
interface descriptive power is central to the attainment of meaning
seems like saying that people couldn't understand each other
until dictionaries and language grammars were documented.  It
seems false.  What exactly is your claim in this area?

> 
> Its possible to have a level 0 network with no common way of describing 
> the message traffic; e.g., email or IM. This work for email because its 
> intended for human eyes primarily.

You seem to be going on the assumption that "describing message
traffic" is somehow critical to the attainment of meaning, and then
by logial extension, critical to the ability to provide service.

Even if that were true, would it matter whether those descriptive
things were happening in-band or out-of-band in your model?
This is one of the ideas I resist.  A third party able to describe the
messages I exchange with you and their meaning does not seem
to constitute a level in our "stack".

> If you are religious about REST and resources then you will see it that 
> way. ;-) However, again, I am trying to be abstract about it. Frankly, 
> I don't agree that seeing everything as resources solves all problems; 
> and I believe that I speak for many when I state that opinion.

My previous comment was actually REST agnostic, but you missed
that. ;-)

The point, which I think you missed, was that constraining a language
to talking only about resources isn't much of a constraint, given we're
basically talking about data processing. Show me an RPC scheme and
I'll show you how it's constrained to describing the manipulation of
resources.

> It doesn't have to be dependent on SOAP. The Web isn't. However, by 
> permitting this stratification, we could model REST on top of specs 
> like SOAP. That may not be the way that it works out in the end, but 
> there is a definite shift in interpretation/commitment going from 
> generic to specific in this way.

I wonder what would be gained by modeling REST on top of
specs like SOAP.  I wonder what would be lost.  But that's off
the topic.

So, in your model then, levels don't signify absolute dependency.
That's in important revelation.

> > Example of the "bending" that is "required"?
> 
> What is it in the semantics of POST that captures the fact that a POST 
> to a particular place denotes a request for information in one case or 
> a request to update a bank balance in another or simply passing the 
> time of day in a third? That is the kind of bending I mean.

I see the ambiguity of POST taken out of any specific context, but
I don't see what's bent in this picture.  Or what you feel you have to
bend.

> It not completely mythical. There is a vast body of work around those 
> verbs; I didn't invent it from nothing.

Is there a URL?  I had too many questions about this to stick even
in a www-ws-arch email, and still do.  Such as

- what makes you think this is not REST?
- how do you explain how this model accounts for action while REST doesn't?

Well, how about two questions for starters? (Three including this
one, damn!;-)

> The real message is this: (IMO) the real relationship between 
> messaging, Web services, REST etc. is the increasing amount of semantic 
> commitment being made.

Semantic commitment?  I don't know how to interpret that
phrase.

> 
> That being stated, it makes very little sense to do battle between the 
> layers; its like arguing that vectors are `better' than reals because 
> everything can be seen as vectors and vectors can do everything that 
> reals can (or vice versa).

I presume this is directed at REST and its "religious followers",
if there is such a thing.  Otherwise, are you doubting the value of
design tradeoffs?  I find them critical to my work.*

Walden

* Even when I'm not, officially, working.  Like now.
Received on Tuesday, 13 May 2003 14:09:39 GMT

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