- How do I locate an OWL ontology?
There are a number of possible sources:
- What are some good ontologies for Semantic Web researchers to use?
Here are some candidates:
- FOAF - A widely-used ontology for describing personal information
- Who's who - A simple vocabulary to describe a person's profile/history.
- SWRC ontology - Defines many classes and properties for modeling a research community. Note, this ontology uses the namespace http://swrc.ontoware.org/ontology#, but this URL cannot be dereferenced. Therefore, I suggest that any files using this ontology import http://ontoware.org/frs/download.php/354/swrc_updated_v0.7.1.owl, so that other tools can locate it.
- ISWC Ontology - The ontology used to describe papers published at ISWC.
- DAML Researchers Ontology
- more?
- What are some good tools for browsing the contents of ontologies?
- Manchester Ontology Browsing Servlet - This form allows you to enter the URL of an ontology and returns a web page that allows you to conveniently browse the ontology by class, property, or individual. Note that this tool appears to have some bugs. In particular, it sometimes reports rdfs:range as the Domain. The WonderWeb Validator appears to be less buggy, and can be used as an alternative for those who are comfortable with the abstract syntax.
- HyperDAML - The main advantage of this tool is that it is available as an online service. Once you find a concept that you are interested in, it is easy to explore related concepts by following the hyperlinks.
- Protégé OWL Plugin - An extension of the ontology editor Protégé with support for editing and visualizing OWL ontologies.
- XML.com Ontology tools survey - This 2004 survey evaluates a wide number of ontology editing tools. You may find it useful in choosing a tool.
- more?
- What are some good tools for building / editing ontologies?
- Protégé OWL Plugin - An extension of the ontology editor Protégé with support for editing and visualizing OWL ontologies.
- SWOOP - A hypermedia-base OWL browser and editor. Includes a debug mode that helps users understand why there are inconsistencies in their ontologies.
- WebODE - A web-based ontology enginering platform. Allows collaborative development, but requires all work to be done online.
- OWL Emacs mode - An OWL mode for the Emacs text editor.
- Protege plugins from CO-ODE - A number of useful plugins, including a graph view plugin and an automatic ontology documentation generator (a la JavaDoc).
- How do I choose a URI for the objects I describe?
This is a tough question and there are currently no standards. If the
object has a homepage (as is common with most people and organizations),
then I currently think a good practice would be to use the URL of this
homepage and then append something like "#Object", "#This" or "#Me". The
SWAT lab has currently adopted the "#This" convention.
Note, that using the URL by itself is generally considered bad practice
because this is considered to denote the page and not the object.
- What naming convention should I use for my OWL file?
The SWAT team currently endorses using the same name as the corresponding
HTML file, except that it should have a .owl extension.
- How do I relate my OWL file to my homepage?
Include a hypertext link on your page with either "OWL data" in the
label or some OWL icon. It is also wise to include a link of the following form, so that browser extension can locate the RDF:
<link rel="alternate" type="application/rdf+xml" href="...">
in the documents HEAD in the meantime.
- How do I ensure that my page is properly "linked in" to the Semantic Web?
The best way to be "linked in" is to use the same URIs that others use when you describe entities. However, this is not always as easy as it sounds. Here are some common problems and solutions:
- What if the URIs don't correspond to URLs that contain RDF information? When this occurs, simply include an rdfs:seeAlso link to the relevant RDF document. This will allow browsers and other tools to locate a more detailed description of the object.
- What if there are multiple URIs for the entity I have in mind? In this case, simply include owl:sameAs statements for each equivalent URI. These links may be followed to find more information, and can be used by reasoners to unify information about the object.
A detailed description of suggested practices can be found in How to Publish Linked Data on the Web.
- What are some good annotation tools?
- Protégé OWL Plugin - This extension of Protégé enables us to edit OWL individuals for Semantic Web markup.
The tool eases the task of creating OWL markup by the visualization of the ontologies and also some convenient features. For example, the tool can choose from the existing individuals as the candidate object for a property statement according to the definition of the property so that we simply need to make a
selection from the list. Alternatively, we can choose to use a new object, in which case the tool will generate the instance for that new object automatically.
As a limitation, strangely, the tool does not accept an URI like http://www.cse.lehigh.edu/~heflin/index.html#me as the rdf:ID for an instance. As a result, We could only use strings like "Jeff_Heflin" instead which are treated as relative to the OWL page.
- SMORE - A tool that allows us to markup documents in RDF using web ontologies. It is simple and easy to use. Main limitation of this tool is that it only accepts literal values for the subject and object of a triple (except for an rdf:type statement). The latest version (v. 5.0) appears to hang when I load ontologies of moderate complexity.
- SWeDE - This a Semantic Web Development Environment, but includes an RDF/OWL editor. I haven't tried it, and would welcome feedback on it.
- Some other possible candidates may be found at
http://annotation.semanticweb.org/tools/ and
http://www.semwebcentral.org/assessment/report?type=category&category=Annotation
- If I choose to write my file by hand, what tools will validate my OWL for me?
- The WonderWeb OWL Ontology Validator - Allows you to select a species of OWL to validate against.
- BBN's OWL Validator - This site appears to be down as of June 6, 2005.
- W3C's RDF Validation Service - All OWL files must also be conformant RDF files. Some OWL validators will fail if the file is invalid RDF; this service can be used to identify the RDF errors. Note, this service will not tell you if the file conforms to a specific ontology or schema.
- Once I've created my OWL file, what can I do with it?
The easiest thing is to use a Semantic Web browser. Here's a few:
- OpenLink Data Explorer - This tool allows to specify the URI of a resource, and assuming the URI is dereferencable, it will retrieve the triples. It's a bit confusing in that it adds alot of its own triples but if you filter the categories, you can find those from your files. The most unfortunate thing about this tool is that you cannot click on an object and browse to it.
- Tabulator - Created by the W3C, this tool can either be run as a Firefox add-on or as a web application. The later requires that Firefox preferences to be set. It is not clear how to use the tool.
- Disco - This is another simple, easy-to-use browser. Note, that unlike the OpenLink browser, when browsing you must enter the URI of the resource of interest, as opposed to the URL of an RDF Web page. It does not appear to be as robust with different ontologies as the OpenLink browser. As of 5/20/2011, this tool no longer works with OWL files that I have published.
- Zitgit Data Viewer - Although the online tool asks for a URI to browse, it apparently doesn't retrieve the URL. It always reports that it "has no information to display about that subject." On a second look, even the provided example doesn't work. (as of 5/20/2011)
- How do I find URIs for things I would like to link to?
It depends on the type of thing that you would like to link to. Here's some suggestions.
- General interest - DBPedia has information on Cities, Countries, Universities, Politicians, Musicians, Films, Books, etc. The easiest way to look for something is to go to a query interface like the iSPARQL one from OpenLink and type:
#service:/sparql
#should-sponge:
PREFIX rdfs:
SELECT DISTINCT ?x ?y
FROM
WHERE {
?x rdfs:label ?y .
?y bif:contains "some name" .
}
- Friends - If your friends have a LiveJournal page, then they have a FOAF profile. To access this page, simply use the URL http://exampleusername.livejournal.com/data/foaf. Unfortunately, LiveJournal does not include URIs for people in its RDF. Thus, you should link to an anonymous foaf:Person and provide a value for their foaf:weblog property. Since this property is inverse functional, it can serve to identify that two description with the same value for it are actually the same person. To provide browsers and search engines the ability to find more information about this person, include a rdfs:seeAlso property that points to the person's FOAF profile as described above.
- Semantic Web Researchers and Events - SemanticWeb.Org has RDF descriptions of people, conferences and tools. Each page has an RDF feed link. From this feed you be able to find the URI for the object (it has the form http://semanticweb.org/id/name). These URIs are dereferenceable, and will return RDF when requested.
- Publications - Faceted DBLP provides RDF pages on each author and publication. These URIs are dereferenceable, and will return RDF when requested.
- Movies - The Linked Movie Database publishes Semantic Web data on movies. The URI for these objects has the form http://data.linkedmdb.org/resource/film/id, http://data.linkedmdb.org/resource/director/id, http://data.linkedmdb.org/resource/actor/id, etc. while the RDF for each of these resources can be found from http://data.linkedmdb.org/data/film/id, http://data.linkedmdb.org/data/director/id, http://data.linkedmdb.org/data/actor/id, etc.