RE: Including Semantics

David

Comments in line ...

David

-----Original Message-----
From: David Booth [mailto:dbooth@w3.org]
Sent: Thursday, February 13, 2003 12:50 AM
To: Burdett, David
Cc: www-ws-arch@w3.org; 'Duane Nickull'
Subject: Re: Including Semantics


David,

WSDL 1.2 addresses semantics in a very limited way by saying that the 
"targetNamespace" of a WSDL document SHOULD identify the 
semantics[1][2].  It doesn't require a document at the end of that 
targetNamespace URL, nor does it say what kind of document it should be if 
there is one.  (That is outstanding TAG issue namespaceDocument-8[3].)\

<DB>Thanks for the info about WSDL which I am not tracking. It occurs to me
that a useful addition to WSDL would be to standardize how semantic meanings
are recorded if required. XML Schema already allows this with its
Documentation structure see which allows for either or both of: a) a local
comment, or b) a uri that provides further information</DB>

If this WSDL 1.2 suggestion is followed, and the semantics are indeed fully 
specified by a document at the end of the targetNamespace URL, then those 
semantics should encompass all of the kinds of semantics that you list.  

<DB>I'm not sure that a single target namespace is sufficient. Data in
documents can have meaning which is independent of the context in which it
is being used, e.g. "an order is a statement of a request for a seller to
provide goods or services" (my definition) which is different from the use
of an order when it forms part of a message and sent to a service, e.g. when
sent to a sales order management service, "an order is a request to the
operator of the service to satisfy the goods in the order" (again my words)
which is has an important difference in meaning</DB>

In 
other words, the semantics of the Web service as a whole would encompass 
the semantics of various transactions, messages and fields within the
messages.

However, since those semantics are written only in terms of the Web 
service, without knowledge of the particular client that may be invoking 
that service, they may have been described in a manner that is somewhat 
parameterized.  
<DB>I think the semantics of a service should be independent of the client
that is invoking it. Otherwise how does the service know what it should do
unless there is some information in the message that tells it what to
do.</DB>

In other words, those semantics may in effect be like a 
semantics template, into which specifics must be inserted to produce the 
semantics for a specific client relationship or interaction.   Thus, it may 
also make sense to have another semantics identifier for a particular 
client-service relationship or interaction (which in turn might reference 
the afore-mentioned semantics template).  The concept of a "CPA" that Duane 
Nickull mentioned[4] looks to me like it roughly corresponds to this idea.

1. http://lists.w3.org/Archives/Public/www-ws-desc/2002Oct/0111.html 
(Semantics proposal)
2. http://lists.w3.org/Archives/Public/www-ws-desc/2002Nov/0010.html (WG 
decision: Agenda item 9)
3. http://www.w3.org/2001/tag/ilist#namespaceDocument-8 (TAG issue)
4. http://lists.w3.org/Archives/Public/www-ws-arch/2003Feb/0044.html

At 04:30 PM 2/12/2003 -0800, Burdett, David wrote:

>Duane asked ...
>
> >>>One missing component I would like to see is semantics.  David - do you
>think there is a way to leverage the semantics of UBL, CCTS for the
WSAG?<<<
>
>Semantics is a whole big topic on its own, but here's my take of the 
>semantic information that you might need to define. Note I'm looking at 
>this from a "business use" perspective:
>
>1. Document Semantics. At the highest level a namespace identifies a 
>document as consisting of a set of fields. Within this there are two 
>additional levels to consider:
>
>   a) Individual fields. Each field needs to be defined, e.g. what does 
> "CustomerId" mean, e.g. is it the ID by which the Customer identifies 
> themselves or the id which the supplier uses to identify the customer?
>
>   b) Fields within a document, e.g. The Customer ID could appear can 
> appear in multiple places in the document - how does its meaning vary 
> depending on where it exists.
>
>2. Context Dependent Semantics. The content of a message can also depend 
>on the context in which it is being used, for example an Invoice in Europe 
>is different from an Invoice in the US as it contains different fields. 
>Similarly an Invoice used in the travel industry contains additional line 
>item information (e.g flight segments) that other industries (e.g. the 
>chemical industry) don't need.
>
>3. Message Semantics. Messages >can< consist of multiple parts where you 
>could describe each "part" as a document. You then need to, in the context 
>of the message, define what each document mean, for example you might want 
>to attach a supplier generated delivery note when requesting a "return 
>materials advice" for some faulty goods. In this case the delivery note is 
>evidence that delivery occured. This is different from its first use when 
>the delivery note informs the buyer of what the supplier has shipped, but 
>not yet delivered.
>
>4. Transaction Semantics. The same message with the same structure and 
>same semantics can be treated differently depending on where it is being 
>sent and the context in which it is being used. For example sending an 
>Order Message to an off-site archival service for archiving would have 
>different meaning than sending the "identical" message to a supplier.
>
>So yes I think you could leverage the semantics of UBL etc, but that is 
>just the start and my best >guess< is that you could use header 
>information in a SOAP message to codify the semantics of the message ... 
>although this sound very non-RESTafarian ;)
>
>Also ... this is a trout hole ... how does the W3C work on the Semantic 
>Web fit in with all of this ;)
>
>David
>
>-----Original Message-----
>From: Duane Nickull
[<mailto:duane@xmlglobal.com>mailto:duane@xmlglobal.com]
>Sent: Wednesday, February 12, 2003 4:00 PM
>To: Burdett, David
>Cc: www-ws-arch@w3.org
>Subject: Re: Layers in the WSA (was RE: [Fwd: UN/CEFACT TMG Releases
>e-Bus ines s Architecture Technical Specification for Public Review])
>
><SNIP/>

-- 
David Booth
W3C Fellow / Hewlett-Packard
Telephone: +1.617.253.1273