It seems to have worked for Derek ...
Judging by the semantic blogs and lists, OWL-S, a vocabulary for describing web services in RDF, seems to be the hot schema of the moment. So, with a view to producing some OWL-S documents for the SchemaWeb web services, I have downloaded the example files and have started reading up the specs starting with Semantic Markup for Web Services.
Firstly congrats to the team for producing high quality documentation. These specs are concise and very readable.
The story I've gleaned so far is that in OWL-S a 'service' consists of three things.
1. A profile that describes what the service does. A high level description that provides a publication and discovery framework for clients and service providers. This is the UDDI bit.
2. A process model that describes how the service works in terms of IOPEs (input, output, preconditions and effects). This is an abstract description of a service.
3. A grounding which describes how to use and physically interact with a service. This covers protocols, message formats, URLs and ports etc. Similar to the 'concrete' bits of WSDL (<binding/> and <service/> elements). In fact WSDL and OWL-S are complementary and are used together to define SOAP web services in OWL-S. So don't throw away your wisdels yet!
Some first impressions and comments.
OWL-S combines the functionality of UDDI and WSDL in one model. +1.
OWL-S allows for reverse directories where clients do the advertising and service providers do the discovering; this is not possible with UDDI.
OWL-S allows 'complex' long running processes 'composed' of many web service calls to be described. This is an obvious advantage over WSDL which has a more highly grained focus and describes only individual web methods. This ability to create and advertise high level services will be good for clients and discovery and also allow third parties to aggregate diverse services and add value.
This is a complex specification. If you have slagged off WSDL in the past as too hard then you might change your mind after looking at OWL-S. And roll on tool support because I don't think there's going to be much hand coding of this baby!
Want to play at Semantic Web?
The .Net RDF parser that drives SchemaWeb is now available under a Creative Commons Attribution-ShareAlike license.
VicSoft.Rdf Parser binaries, source and documentation are at:
This lightweight smush and query software component was developed on Windows. However it should run with Mono for those who work on the sunny side although this is un-tested.
Thanks to all for the feedback and support received in the last week since the launch of SchemaWeb.
New features since launch include 'Schema of the Week' starting off with the mighty RSS 1.0. Also SchemaWeb is now hosting Dr Ont's Semantic Spout, a blog which will carry SchemaWeb news and RDF matters in general.
VicSoft (makers of Buddy Browser FOAFware) announce the launch of SchemaWeb, an on-line directory of RDF schemas expressed using the RDFS, OWL and DAML+OIL schema vocabularies.
SchemaWeb provides (hopefully) a one stop shop for developers and designers working with RDF. It gathers schema data and meta-data in a single portal and offers both on-line forms and web services for access to RDF schema information by both human users and RDF software agents.
SchemaWeb is at:
Your feedback is welcome.
For the first time since 1997 and the first Microsoft XML toolkit / parser, I have had to hack into XML files using regular expressions (arrrrrg!) in order to get a valid XML document to load into Microsoft XML tools.
An example of this type of XML is:
<!DOCTYPE root [
<!ENTITY ns "http://www.some.com/schema">
The author of this type of XML is using a general entity to represent the default namespace uri. Both XmlDocument and XmlValidatingReader barf on this file with an error of:
System.ArgumentException: Prefixes beginning with "xml" (regardless of whether the characters are uppercase, lowercase, or some combination thereof) are reserved for use by XML.
So is this a valid XML document? Although using general entities in this way seems to be pushing the envelope a bit (Are namespaces part of the XML data or do they sit in a layer above the data?), I have seen quite a few examples in this style on the W3C site so I assume it is valid. So in order to deal with this type of XML, I have had to write code using tedious regular expressions to manually find and replace the offending entities prior to loading into .Net XML classes.
Which brings me to my point and request. How do I report this bug to the MS XML team? I have looked on Technet and MSDN but cannot find a way to do this.
Wow, two very hot articles on XML.com.
Mark's piece on Atom and RDF (sorry - we failed the audition) and Kendall's on OWL.
So Atom is XML with a maintained, normative XSLT port to RDF. Better than nothing I suppose and most Atom providers will transform on the server and provide both XML and RDF feeds.
Mark, perceptive chap that he is, drills down to the two reasons why RDF won't be on Fame Academy next week. Tool support and RDF / XML syntax.
Mark is down on the Semantic Web. Well I never thought of the Semantic Web as some ethereal, elusive concept dreamt up by some PR brain farter. To me it is just code; a way to code a bit of 'intelligence' into our software applications. And OWL, as Kendall reports, is a step towards this.
Sam Ruby has a moan about RDF / XML. Some people just don't understand.
Also Edd Dumbill has a little gripe with RDFDrive, the only compliant RDF parser available for the .Net platform so I suppose beggars can't be choosers.
'Why all the interfaces', says Edd? Well, interfaces are cool. It means I can develop a parser that will query an in memory RDF graph and a parser that will query a database triples store against the same IRdfParser interface. I can then pass either parser to a application specific component, say a FOAF processor regardless of the internal implementations.
His other gripe is with the node based query model which I agree is clunky. Mine main gripe with RDFDrive is the fact that it uses a DOM instead of an .Net XmlReader to deserialise the XML into triples. This is a real performance killer and resource eater when working with RDF files over the internet. That's why I'm presently extending and upgrading Jason Diamond's excellent RdfReader to the latest Working Draft spec and then going to use it as the basis for a proper parser. You know, the one with that nice graph.GetStatements(subject, predicate, object) interface like RAP. Is there a better query interface? Please please let me know before I start!
One new feature of the Working Draft that I won't be tackling in a hurry is rdf:parseType = "Collection". Have you seen the triples that this is supposed to produce? And while we are talking syntax, why oh why is RDF / XML syntax so complicated? Any reasons or excuses for this would be appreciated because quite frankly, I just don't understand.
So hang on there all .Net RDF heads (all 2 of you), I will be releasing VicSoft.Rdf.RdfParser + source code in September.
Has XML lost its buzz for you now that it's established and mainstream? If you are techie minded and like to bend you brain working with cutting edge technologies, then try the FOAF and RDF clubs on Ecademy. RDF is a bit like ..er.. XML and may be the framework for the next big thing, the all knowing and all seeing Semantic Web.
Dear Doctor DotNet, I have a problem that you might be able to help with. I am currently extending an ASP.Net application and have noticed that on many pages some idiot has commented out both Option Explicit On and Option Strict On. I just can't bring myself to uncomment these however much I try. Is this plain lethargy or a (professional) attitude problem or just the dread of the two days work that it will probably take to fix the inevitable bugs and sort out the bloody mess. What should I do? And why did MS bring these heinous incitements to bad programming from VB6 into VB.Net? I prefer to use the beautiful C# any day.
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