Re: Vocabulary (ontology) URI vs namespace

Stuart Williams in cc who is not subscribed to this list gave me the green
light to forward his thoughts, copied below.
In answer to the last remark about the ontology and ontology document
distinction, Dave Reynolds pointed to the OWL 2 specification
http://www.w3.org/TR/owl2-syntax/#Ontology_IRI_and_Version_IRI

As Stuart, I'm not sure this specification totally clarifies the
ontological status of an ontology. As written before, using FRBR to make
distinct the ontology as an abstract work and its various expressions and
manifestations seems the way to get out of those misty territories.

Bernard

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Stuart Williams wrote :

FWIW I think that there are two consistent views and two sets of associated
URI patterns.

View 1: An Ontology and the document resource(s) that describe it are
different things and therefore need different URIs.
------
For so-called "#-ontologies":
    Namespace Prefix: http://{authority}/{vocabulary-path}#
    Base URI: http://{authority}/{vocabulary-path}

    Ontology Document generic URI: http://{authority}/{vocabulary-path}
    Ontology URI: http://{authority}/{vocabulary-path}#

    Base relative terms references    #{term} (but beware of same-document
references RFC 3996 section 4.4)

For so-called "/-ontologies":
    Namespace Prefix: http://{authority}/{vocabulary-path}/
    Base URI: http://{authority}/{vocabulary-path}/

    Ontology Document generic URI: http://{authority}/{vocabulary-path}
    Ontology URI: http://{authority}/{vocabulary-path}/

    Base relative terms references    {term}

In both cases the namespace URI (which as a namespace has no significance -
it's just a device to abbreviate a URI) and Ontology URI are identical.
The base URI for #-ontologies matches the ontology document (to make
relative referencing useful) and for /-ontologies matches the ontology
itself (again to make relative referencing useful).

View 2: An owl serialisation is merely a representation of an Ontology...
there is only one (generic) resource here (and its ttl, nt, rdf etc.
variants)
------  ie. the document and the ontology are one and the same thing.

For so-called "#-ontologies":
    Namespace Prefix: http://{authority}/{vocabulary-path}#
    Base URI: http://{authority}/{vocabulary-path}

    Ontology Document generic URI: http://{authority}/{vocabulary-path}
    Ontology URI: http://{authority}/{vocabulary-path}

    Base relative terms references    #{term}

For so-called "/-ontologies":
    Namespace Prefix: http://{authority}/{vocabulary-path}/
    Base URI: http://{authority}/{vocabulary-path}/ [1]
           http://{authority}/{vocabulary-path}  [2]

    Ontology Document generic URI: http://{authority}/{vocabulary-path}
    Ontology URI: http://{authority}/{vocabulary-path}

    Base relative terms references    {term}   [1]
                                      ./{term} [2]

For the '/-namespace' there is a tension between whether to match the base
URI with the natural ontology/document URI which makes for slightly more
awkward relative referencing match it with the namespace name which makes
for more 'natural' relative referencing.

In either view it is the ontology and document (if you take the position of
them being different things) identifiers that are crucuially important. The
base URI and namespace URI are just devices for URI shortening and that can
be got right (even if not always at first attempt - folks can miss that
resolving relative references is not simple concatenation).

For myself - I have never been quite able to commit (universally) to an
ontology and its describing document being the same thing. I'm open to the
possibility... but I haven't found anything in the OWL documents that
resolves that for me (maybe haven't look hard enough). So I tend to be a
view #1 /-ontologies sort of a person - misguided though I may be :-).

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