Hello Simon,
the # at the end of this particular namespace is indeed unusual, and the
authors may want to change this before publishing the final version -
most other ontologies use the graph URI without # for the owl:Ontology.
Anyway, TopBraid can handle those without problems. I have created a
file that imports http://www.w3.org/ns/locn# and then used the Download
button in the Imports view to get a local copy as a .ttl file. I can
then open the Turtle file without problems. Note that the classes of
this ontology show up under rdfs:Resource, so that is probably why you
are not seeing any contents if owl:Thing is the root of your class tree?
HTH
Holger
On 12/20/2013 11:12, Simon Cox wrote:
TopBraid appears to enforce an assumption that the Ontology URI is the
same BaseURI.
This is not strictly required by the relevant standards, and may not
followed by some published vocabularies, which
(a) don't define a baseURI (in which case I think it defaults to the
source URL or filename)
(b) set the ontology URI to a different value to the Base URI.
Today I encountered this with the newly announced W3C Location
vocabulary http://www.w3.org/ns/locn .
After a lot of preliminary work, they have now moved the vocabulary
into what is expected to be the permanent namespace
http://www.w3.org/ns/locn# . So even though the vocabulary has not yet
been finalized, it is now available for testing, and the intention is
that this is the URI that it will be published at.
I have tested the W3C deployment in TopBraid by creating a stub
ontology that merely owl:imports from the web location. That goes
fine. However, TopBraid does not allow me to open it directly. I
retrieved the vocabulary and saved it as a file to a location from
where I can access it within TB. When I attempt to open it I get the
following error:
"Can not open file locn.ttl.
Reason: The file does not contain a valid base URI and cannot be
opened. ..."
Here are the relevant snippets from this vocabulary in TTL and RDF/XML
formats:
Turtle:
@prefix locn: <http://www.w3.org/ns/locn#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix vann: <http://purl.org/vocab/vann/> .
@prefix voaf: <http://labs.mondeca.com/vocab/voaf#> .
locn: a voaf:Vocabulary,
owl:Ontology ;
vann:preferredNamespacePrefix "locn"^^xsd:string ;
vann:preferredNamespaceUri "http://www.w3.org/ns/locn#"^^xsd:anyURI .
Right - no baseURI, so the base would default to the filename. But the
Ontology URI is different, in fact the ontology URI is the same as the
locn: namespace - i.e. it has a trailing #.
Getting the RDF/XML version we find
RDF/XML:
<rdf:RDF xml:base="http://www.w3.org/ns/locn";>
<owl:Ontology rdf:about="http://www.w3.org/ns/locn#";>
<rdf:type
rdf:resource="http://labs.mondeca.com/vocab/voaf#Vocabulary"; />
<vann:preferredNamespaceUri
rdf:datatype="http://www.w3.org/2001/XMLSchema#anyURI";>http://www.w3.org/ns/locn#</vann:preferredNamespaceUri>
<vann:preferredNamespacePrefix
rdf:datatype="http://www.w3.org/2001/XMLSchema#string";>locn</vann:preferredNamespacePrefix>
</owl:Ontology>
</rdf:RDF>
So in this case the baseURI is declared, but this is different to the
Ontology URI.
When I attempt to open this directly I get no error, but also no
content visible in TBCME.
Running experiment creating a new ontology via TBCME's
File->New->RDF/OWL File dialogue, while it is possible to make the
baseURI different to the filename, TB does not seem to allow the
BaseURI and the Ontology URI to be different.
Until now I had gone along with the TB assumption, but now we seem to
have hit a wall. If I were to be engaging with a community that was
not following the TB assumption, then I would not be able to use TBCME
for ontology development. W3C is not just any community, so if this is
the direction they are heading, then this could be a problem for
TopBraid. And in this case I know the editors of this spec, and was
invited to take part in the ontology development. I was unable to at
this time, but would expect to engage more in the future.
Simon
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