Re: [WSDL] Message Typing: Example and Comments

Mithun,

Thanks for the example.

On Feb 8, 2004, at 4:43 PM, Mithun Sheshagiri wrote:

> Hello all,
>             Some time back, I wanted to deploy a set of web services 
> which uses RDF/XML
> for input and output and I essentially adopted the technique suggested 
> by Bijan in his
> first question. Below is a service that takes in a keyword and returns 
> a list of items
> that match the keyword. There are certain problems with this approach 
> though. The example
> service takes in a keyword as an input and produces a list of Items in 
> an ItemList.
>
> - keyword - string
> - ItemList
>         - member
>                 - Items
>
> Even for such simple class descriptions, the schema is obscenely 
> verbose. I had to embed the schema
> definitions for keyword and ItemList using the <xsd:choice>. If anyone 
> has a more concise way of describing
> this thing, please let us all know.

I tend to aim for simpler serializations (like so called "NTriples in 
RDF/XML"). If you are really trying to schema check your messages for 
correct classes....well, that's tricky :)

> Also, it will interesting to see if one could design a tool that takes
> in class definitions in OWL and convert them into an XML schema.

Perhaps, though I'm very skeptical about this. It doesn't eliminate the 
problem of incomplete information (or too much information).

[snip]
> The service accepts a keyword and outputs ItemList. The SOAP response
> looks like this:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <soapenv:Envelope
> xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
> xmlns:xsd="http://www.w3.org/2001/XMLSchema"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
>   <soapenv:Body>
>    <RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
>     <ns2:ItemList ns1:ID="instanceOfItemList"
> xmlns:ns1="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> xmlns:ns2="http://effects.com/">
>      <ns2:member ns1:resource="http://thisone"/>
>      <ns2:member ns1:resource="http://thistwo"/>
>     </ns2:ItemList>
>     <ns3:keyword xsi:nil="true" xmlns:ns3="http://effects.com/"/>
>    </RDF>
>   </soapenv:Body>
> </soapenv:Envelope>
> As can be seen, the xml fragment within the <Body> element is valid 
> RDF/XML syntax if one moves the xsi namespace declaration into the RDF 
> element.
> Incidentally, this message is generated by Apache AXIS and some 
> hacking probably can remove the <keyword> element in the above message 
> altogether.

Would you be happy (-ier, less happy) if you just described the service 
as consumign an ns3:keyword and returning an ns2:ItemList? Even if 
there were extraneous (or missing) information in the reply?
[snip]

> We think that the industry might not be very interested in services 
> that produce RDF/XML as output; especially the ones who have already 
> deployed web service based systems (that use XML) and have a mature 
> infrastructure for managing and using web services. We probably should 
> look at ways by which semantics could be plugged-in to an existing 
> system. This is also OWL-S position (XSLT templates to convert XML to 
> RDF/XML) as Bijan has mentioned.

Of course, I'm not just interested in what industry in general wants :) 
The real issue is there a good reason to allow OWL classes as 
descriptors of messages. Does anyone want this?

> However, when RDF becomes an houseold name :) , maybe people might be 
> interested in services that produce OWL entailments as the output.
[snip]

If they are entailments, then they probably could be conveyed by some 
serialization (i.e., the return type be rdf:RDF). But again, this makes 
it rather difficult to verify messages.

Thanks for the reply.

Cheers,
Bijan Parsia.

Received on Sunday, 8 February 2004 18:38:35 UTC