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RE: Semantics of WSDL vs. semantics of service

From: Jacek Kopecky <jacek.kopecky@deri.org>
Date: Mon, 20 Mar 2006 20:32:33 +0100
To: "Shi, Xuan" <xshi@geo.wvu.edu>
Cc: public-sws-ig@w3.org
Message-Id: <1142883153.19760.21.camel@localhost>


if you send what you described below, my service will fault because it
expects element <symbol>exmp</symbol>, not <CompanyName> etc.

What I'm getting at is that the provider chooses what the service
accepts, and two providers will generally choose two different formats.
It all can be written down as doService(String):String, but that only
tells you that you that there is a request and that there is a
response*. However, to successfully invoke my service, you need to know
what I expect. You call it service description template, we call it

(*)Let's not even go into different message exchange patterns here.

Maybe your templates are easier for people on some simple cases, but
that has no bearing on what we are trying to do here. SWS is about
automating WS usage. If I ask my computer how much is 3+4, it should be
able to find suitable services (addition), choose the best one (cheapest
or fastest), adapt itself to the syntactical requirements of the chosen
service (like two ints called x and y, or two doubles called a1 and a2),
form the correct message and send it to the service, then parse the
response (int z, or double rslt) and give me the result 7.

For all of this, WSDL is equivalent to your description language of
choice, and with SA-WSDL we want to be able to say that operation "add"
will compute the sum of the two numerical arguments, and that elements x
and y are those arguments, and that element z is the sum.

Do you have an issue with this? If so, what is the issue concretely?


On Mon, 2006-03-20 at 12:44 -0500, Shi, Xuan wrote:
> Jacek,
> I know there's a plethora of functions that are provided by Web services,
> and we have to consider data format issues, etc. as service providers. What
> I stressed is that, the interface designed for requesters can be different
> from that for the providers. When service requesters send a request to
> service providers through the standardized interface
> (doService(String):String), service providers will then differentiate which
> data types are specified within the service description document.
> For example, in a stock quote service, I send you the following elements in
> the XML document,
>   <s:element minOccurs="0" maxOccurs="1" name="CompanyName" type="s:string"
> /> 
>   <s:element minOccurs="0" maxOccurs="1" name="StockTicker" type="s:string"
> /> 
>   <s:element minOccurs="0" maxOccurs="1" name="StockQuote" type="s:string"
> /> 
>   <s:element minOccurs="0" maxOccurs="1" name="LastUpdated" type="s:string"
> /> 
>   <s:element minOccurs="0" maxOccurs="1" name="Change" type="s:string" /> 
>   <s:element minOccurs="0" maxOccurs="1" name="OpenPrice" type="s:string" />
>   <s:element minOccurs="0" maxOccurs="1" name="DayHighPrice" type="s:string"
> /> 
>   <s:element minOccurs="0" maxOccurs="1" name="DayLowPrice" type="s:string"
> /> 
>   <s:element minOccurs="0" maxOccurs="1" name="Volume" type="s:string" /> 
>   <s:element minOccurs="0" maxOccurs="1" name="MarketCap" type="s:string" />
>   <s:element minOccurs="0" maxOccurs="1" name="YearRange" type="s:string" />
>   <s:element minOccurs="0" maxOccurs="1" name="ExDividendDate"
> type="s:string" /> 
>   <s:element minOccurs="0" maxOccurs="1" name="DividendYield"
> type="s:string" /> 
>   <s:element minOccurs="0" maxOccurs="1" name="DividendPerShare"
> type="s:string" />
> although, they are all in string data types, but once you process the
> request, you understand which one is a string, which one is an integer or
> double data type, which one is a date data type, in your programming. In
> this case, you handle all such conversions on your server side. However, for
> the service requesters, they just need to send you such a request document
> without considering the data type issues.
> As I demonstrated before, I can invoke both geocoding and data conversion
> services through such a standardized interface. As a service provider, I
> know which elements are string data types in the programming, and which ones
> are double data types. The requesters do not need to care about such issues.
> In that example, I showed that two different kind of functions in different
> web services can be implemented by one interface. That's the same analogy in
> comparing to the case of consuming electricity via standardized plug and
> receptacle. In my dissertation research, I developed different kind of Web
> services for geocoding, data conversion, data processing, spatial query and
> analysis, integrated mapping, etc. ALL of them just have the same interface
> (doService(String):String). 
> Please describe any of your use cases, and let's see if such a request can
> be sent through (doService(String):String) interface to the service
> provider. As I told Carine before, the service description template is
> pre-defined by service provider. Supposed you are a service provider and you
> pre-define a service description template. If I send you such a request
> following your pre-defined templage, can you handle such a request to
> differentiate whatever data types embedded in such a document to match those
> in your programming language? I wish you could try it first to see if it is
> feasible to develop standardized plug and receptacle interfaces for all of
> your services and functions.
> Best wishes,
> Xuan
> -----Original Message-----
> From: Jacek Kopecky
> To: Shi, Xuan
> Cc: 'Bijan Parsia '; 'Carine Bournez '; 'public-sws-ig@w3.org '; 'Battle,
> Steven '
> Sent: 3/20/06 11:47 AM
> Subject: RE: Semantics of WSDL vs. semantics of service
> Xuan, 
> the problem is that Web Service interfaces are not so well standardized
> as electrical plug interfaces, and that's because there's a plethora of
> functions that are provided by Web services, as opposed to the one
> function provided by the electricity company.
> In particular, I don't expect that the interface of my stock quote
> service should match the interface of your address lookup service. Even
> if the operation is the same (doService(String):String), we will differ
> on the data formats and on what we actually perform. WSDL describes the
> data formats and WSDL-S tries to point to a description of what we
> actually perform.
> I'm afraid you have a simplified or idealistic view on what Web services
> (should) look like.
> Jacek
> On Mon, 2006-03-20 at 09:56 -0500, Shi, Xuan wrote:
> > It seems you all just ignore the title of this thread as "Semantics of
> > vs. semantics of service" and Bijan just could not answer my question
> to him
> > as why do I need to care about how many bindings he
> > has for one operation? Or, why do I need to understand the semantics
> of his
> > WSDL document?
> > 
> > Given a simple example, we are all the consumers or service requesters
> of
> > certain electricity company. Do we need to care about the
> infrastructure and
> > the framework of the electricity company before we consume such
> service? Do
> > we need to care about how many bindings the electricity company has,
> and,
> > how they switch to any other bindings to maintain its operations to
> support
> > the service it provides? Definitely not!
> > 
> > As service providers, can we give more consideration for our service
> > requesters? We can consume the electricity in the same interoperable
> > appraoch because every plug and receptacle are all standardized. In
> that
> > way, the service requesters do not need to care about your complex
> > infrastructure, framework, logics, etc. People access "Web" services
> in the
> > same situation.
> > 
> > So, please encapsulte all troubles into your server side development.
> > Service requesters only need one standardized receptacle so that they
> can
> > use any interoperable plug to consume the service with little
> question. They
> > don't need to know how many bindings you have to maintain your single
> > operation. We are service providers, not trouble makers.
> > 
> > -----Original Message-----
> > From: Bijan Parsia
> > To: Jacek Kopecky
> > Cc: Carine Bournez; public-sws-ig@w3.org; Battle, Steven
> > Sent: 3/20/06 8:09 AM
> > Subject: Re: Semantics of WSDL vs. semantics of service
> > 
> > 
> > On Mar 20, 2006, at 5:39 AM, Jacek Kopecky wrote:
> > 
> > > Hi Steve,
> > >
> > > while the charter does not directly support embedded semantic
> > > annotations, I think the issue is still open and up for discussion
> by
> > > the WG.
> > 
> > I went back and looked and the Scope section is a bit broken (as 
> > evidenced by Steve's quote):
> > 
> > """The Semantic Annotations for WSDL Working Group is chartered to 
> > define one or more properties of WSDL 2.0 components to point to 
> > additional semantics to concepts represented by those components, e.g.
> > interface, operation, endpoint. Additionally, the Working Group may 
> > define annotations to the schema structure to point to external 
> > semantics.""""
> > 
> > "point to additional semantics to concepts" just doesn't parse. 
> > Additional semantics *for* concepts represented?
> > 
> > I confess to hating the term "external semantics". C'mon.
> > 
> > > I for one see some use cases where embedding the annotations would
> be
> > > useful, and I can see at least two ways of embedding them: put a
> whole
> > > semantic description
> > 
> > I go back to a fight I had in SWSL. What's a *non* semantic
> description?
> > 
> > >  document somewhere in the WSDL document (like we
> > > put schemas in the <types> section) and then the annotations will
> > point
> > > into the document; or put the full annotations themselves on the
> spot,
> > > instead of referring to them.
> > 
> > How are the "semantics" to be realized? Via some sort of statement 
> > (e.g., axioms in some formalism). So let's say I have a set of concept
> > and property names, but no further axiomization. And I want to say of 
> > some operation that is has at least one P relation to a C. Now since 
> > there *is* no other axiom, this characterized the terms entirely (thus
> > far). May I inline that? It seems like I should be able to. 
> > Alternatively, I could require that I always coin a name for these 
> > intermediate expressions (but why?).
> > 
> > (Note that originally I interpreted the discussion as requiring *all 
> > parts* of the annotation to be outside the WSDL document, a la OWL-S. 
> > There are reasonable reasons for doing this (including supporting
> third 
> > party and alternative annotations seamlessly. Technically, I guess
> this 
> > is not ruled out by the current charter since the concrete syntax of 
> > the component properties could be or be required to be in a separate 
> > document.
> > 
> > > While the second option can be seen as out of scope as defined in
> the
> > > charter, at least the first option should be available to us. 8-)
> > 
> > I find the Out of Scope more disturbing:
> > 
> > """discuss expression of Web services constraints and capabilities, 
> > including precondition and effect."""
> > 
> > Why? And how can this be at all narrowed? I mean, from the scope, " 
> > could have different meanings: calculation of tax on a product, 
> > calculation of income tax, etc. " Aren't these expressions of 
> > capabilities? (I recognize that constraints and capabilties are a term
> > of art standing for "policy", but still.)
> > 
> > Cheers,
> > Bijan.
> > 
> > 
Received on Monday, 20 March 2006 19:32:57 UTC

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