Ho Ho. Funny you should mention this. I was just complaining about it
yesterday. In this snippet it is me first, alternating with Richard
Cyganiak. (The "weirdness" that Jim is referring to is that even
requests for content-type: application/rdf+xml to the foaf URL return
html)
For example I am terminally confused by FOAF. What does the name
"http://xmlns.com/foaf/0.1/"; refer to?
That's the FOAF vocabulary specification. A document, since GET
returns 200. It's available in HTML format, and may or may not be
available in other formats.
What does this mean (from foaf rdf)? <rdfs:isDefinedBy
rdf:resource="http://xmlns.com/foaf/0.1/"/>
The subject is defined by the FOAF vocabulary specification.
rdfs:isDefinedBy doesn't constrain the defining document to any
particular format.
How does a SW agent get the rdf for http://xmlns.com/foaf/0.1/
Organization ?
It can't get the RDF since the FOAF folks have do neither GRDDL nor
a <link> header nor content negotiation. FOAF gets away with this
because everybody has to support FOAF, and so everybody just
hardcodes the URL to their RDF.
Guess FOAF isn't quite getting away with it :) I'm not sure why they
ever thought they could.
Emanates from a criticism I make about content negotiation being bad
semantic web practice.
http://lists.w3.org/Archives/Public/semantic-web/2007Apr/0060.html
It's my turn to respond. I'm reading about Content-Location headers,
from RFC2616 - HTTP1/1. Here's a bit I'm currently trying to digest.
It's not going down very well.
The Content-Location value is not a replacement for the original
requested URI; it is only a statement of the location of the
resource corresponding to this particular entity at the time of the
request. Future requests MAY specify the Content-Location URI as
the request- URI if the desire is to identify the source of that
particular entity.
A cache cannot assume that an entity with a Content-Location
different from the URI used to retrieve it can be used to respond
to later requests on that Content-Location URI. However, the
Content- Location can be used to differentiate between multiple
entities retrieved from a single requested resource, as described
in section 13.6.
Section 13.6 discusses the "Vary" header. More fun (but only if you
care about what URIs refer to).
-Alan
On Apr 11, 2007, at 9:34 PM, Jim Hendler wrote:
[snip]
However, I think the bigger issue here is that there were (and I
believe still are) some weirdnesses in the machine readability of
the FOAF namespace ( http://xmlns.com/foaf/0.1 ) and that a number
of systems have problems with it (I notice if I try to load it
directly into SWOOP I still get XML parsing errors). Lots of
systems have done various work arounds for this -- so when you
report your error to the Protege mailing list, you might also send
it to the FOAF one, we've been complaining about this for a couple
years now, maybe if some other folks yell as well we can get it so
that the most used Semantic Web vocabulary will actually conform to
the standards it promotes :-)
-JH
On Apr 11, 2007, at 7:35 PM, Noah Cohen wrote:
I have protege version 3.2.1 build 365 and JDK 1.5.0
If I run this ontology through a verifier, it verifies the
ontology seemingly without a problem.
If i try to load the ontology directly from http://
metacognition.info/ontologies/problem-oriented-medical-record.owl
I get some very interesting error:
WARNING: [ProtegeOWLParser] Warning: Trying to add import for
external resource:
http://purl.org/dc/elements/1.1/ --
DefaultProtegeOWLParserLogger.logWarning()
INFO: [ProtegeOWLParser] Importing http://purl.org/dc/elements/
1.1/ (from Redire
ct to http://protege.stanford.edu/plugins/owl/dc/protege-dc.owl
<http://protege.stanford.edu/plugins/owl/dc/protege-dc.owl>)
The resource p1:chime has the rdf:type http://xmlns.com/foaf/0.1/
Person which is
not a class but a
edu.stanford.smi.protegex.owl.model.impl.DefaultRDFUntypedRes
ource
Suggestion: In many cases the problem is a missing owl:imports
statement to the
classes file which defines the correct type of http://xmlns.com/
foaf/0.1/Person
It seems to me that it cannot distinguish the foaf Person class,
with or without the foaf imports statement. If someone could
please assist here, it would be of great help. Thank you in
advance,
Noah
