- From: Bijan Parsia <bparsia@isr.umd.edu>
- Date: Sun, 8 Feb 2004 18:38:29 -0500
- To: Mithun Sheshagiri <mits1@cs.umbc.edu>
- Cc: skw@hp.com, public-sws-ig@w3.org
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