Jeff Thompson wrote: > At the beginning of SMW development, the idea was that, to make everyone > happy, anyone could create any property that they want and give it whatever > meaning they want in their wiki. That's great for making everyone feel > included (even the wiki users who just want to jump in without thinking > about what they are doing). > > But as soon as SMW has to do inference, even the basic inference for > transitive and inverse properties, then this requires not only a > syntax, but also a semantics. Some people don't like (or don't understand) > the semantics developed for OWL, but at least it is well-defined. > > Does SMW use the semantics defined for RDF/OWL by default?
SMW is "just" PHP code that parses wiki annotations and makes DB queries. It implements some useful semantics, e.g.: * querying for category membership also finds members of subcategories, * querying for a property finds also finds pages with its subproperties * querying for a page also finds #REDIRECT pages. but not (currently) others (transitive properties, identical properties, etc.). So there's no "default" semantics, just code, though I'm sure the main developers were guided by ideas in RDF/OWL. Special:ExportRDF does use RDF, RDFS, OWL, and XSD semantics to represent the annotations in SMW; export some pages and see! As you note, many SMW sites don't care about this. As we've discussed on the mailing lists, other sites do care about the semantics that RDF Export "promises", especially when it comes to MediaWiki categories. > If a wiki > user wants a different semantics (for what defines equivalent topics, etc.) (Equivalent topics isn't a good example because its sort-of covered by making one page a #REDIRECT to another, or to link to an external concept see <http://semantic-mediawiki.org/wiki/Property:Equivalent_URI>.) > does SMW support a language for them to define it (pretty difficult)? FYI, to me SMW 1.1's "language of semantics" is, roughly: * MediaWiki's articles, categories, and #REDIRECT * SMW's property annotations * and SMW's 8 special properties <http://semantic-mediawiki.org/wiki/Help:Properties_and_types#Special_properties> That's insufficient to define semantics for things like transitive, inverse, broader, etc. You're free to add additional properties and categories to your wiki representing any semantics, but they won't mean anything to SMW, and it's up to you to make your queries respecting them. You can see lots of experiments along these lines on the sandbox site, e.g. check out http://sandbox.semantic-mediawiki.org/wiki/Category:Transitive_relation One thing you can do is use http://semantic-mediawiki.org/wiki/Help:Import_vocabulary to associate terms in your wiki with an external ontology. Then RDF export will use that ontology in place of <property:Your_name>. The classic example of this is importing FOAF so Property:Name can export as <rdf:RDF ... xmlns:foaf="http://xmlns.com/foaf/0.1/"; > <foaf:name> which means something to Sir Tim's "Semantic web"; instead of <!ENTITY property 'http://semanticweb.org/id/Property-3A'> <property:Name> which doesn't mean anything outside your wiki. At one point I wanted to take all the properties that people invented in experiments with ontologies on the old ontoworld.org site and say [[Imported from::owl:inverseOf]], [[Imported from::skos:narrower]], etc. But as Markus wisely pointed out, doing this would suggest that SMW supports these features. > You see where I'm going with this question. Doesn't SMW need to get > past the "anything goes" and officially commit to some well-developed > semantics > such as OWL? What's wrong with what I've described above? What would you like to see instead? I imagine that as SMW does support additional features of ontologies, each will effectively have certain semantics in its PHP implementation and promise certain semantics in RDF export, just as say <http://semantic-mediawiki.org/wiki/Property:Subproperty_of> does now. I hope this simplistic overview helps. BIG DISCLAIMER: I haven't inspected the new features in SMW 1.2, nor have I used SMW with SMW_RAPStore (RDF API for PHP) instead of the default SMW_SQLStore. As ever, I'd love to hear of people's experiences using SMW with external ontologies. Some of these topics are touched on by http://semanticweb.org/wiki/Help:Suggestions , which people can edit. Regards, -- =S Page ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Semediawiki-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/semediawiki-devel
