W3C home > Mailing lists > Public > www-ws-arch@w3.org > September 2002

RE: Representing HTTP in arch diagrams

From: Champion, Mike <Mike.Champion@SoftwareAG-USA.com>
Date: Thu, 19 Sep 2002 15:30:22 -0600
Message-ID: <9A4FC925410C024792B85198DF1E97E40400D4FB@usmsg03.sagus.com>
To: Mark Baker <distobj@acm.org>
Cc: www-ws-arch@w3.org



> -----Original Message-----
> From: Mark Baker [mailto:distobj@acm.org]
> Sent: Thursday, September 19, 2002 5:08 PM
> To: Champion, Mike
> Cc: www-ws-arch@w3.org
> Subject: Representing HTTP in arch diagrams
> 
>
> I don't know what you mean by "knowledge of the interaction 
> mechanism".
> And why would you need to hard code important URIs?  I don't follow.

The "conventional wisdom" would go something like this:  In the
human-readable Web, interaction is done by typing in URLs or clicking on
hyperlinks, discovery is done by reading the text associated with hyperlinks
or using a search engine, and publication is done "by hand" with HTTP
PUT/POST, FTP, or whatever.    For the machine-processable Web, discovery
and description are more problematic -- one needs to either hard-code the
actual URLs, or code up the rules for building specific requests into a URI
and some way of determining the server to send HTTP request to.  Thus, SOAP
was devised as a standardized and programmer-friendly way to do the
interaction, WSDL was devised as a way to rigorously describe the format of
SOAP requests and responses, and various discovery mechanisms are being
devised to make it possible to find WSDL descriptions.  Furthermore, SOAP
has become protocol independent, so HTTP is not necessarily a part of the
interaction.

So, how do you suggest we "draw" HTTP into the picture?  (Especially
considering that it is not strictly speaking necessary in the SOAP/WSDL
world?) I like the idea of explaining how  SOAP/WSDL evolved to address the
challenges that people had trying to automate Web-style interactions without
a human in the loop.  One can do things with HTTP alone, of course  --a
point you might have made once or twice :-) -- but then how does description
and discovery work?  I'm just asserting that this is generally done with
application-level code rather than declarative languages such as WSDL in a
RESTful application.  Do you disagree?  

Anyway, that's what I meant by "hard coded": URIs are generated by
application code rather than SOAP messages generated from a declarative
description.  Maybe that's not helpful, since of course one could infer the
URIs from RDF metadata or whatever, and the declarative/procedural issue is
orthogonal to all this.  But as a practical matter in today's technology, I
do think that WSDL evolved to help people avoid the hassles of "hard coding"
URI generation logic.
Received on Thursday, 19 September 2002 17:30:56 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 3 July 2007 12:25:06 GMT