Hi Kevin,

Thanks for your thoughts. It does seem a bit of a hack the way I am suggesting - more elegant solutions are welcome but I am not sure we can get the hierarchy in the namespace.

The classes would still be part of a regular inheritance hierarchy but you wouldn't see it in the namespace.

The only way you would see the hierarchy is if you had namespaces that went something like this:

http://rs.tdwg.org/ontology/BaseThing/MyClass/MySubclass/MySubSubClass/myproperty

Kind of like an xpath down the hierarchy for every concept. I am not sure how you would then handle targetNamespaces in XML Schema.

I believe most people in the semantic world seem to have a namespace per ontology and no indication of the class structure within the ontology from the namespaces.

I am curious about what a huge list of classes is - I have a general question in the back of my mind about how big people think the TDWG ontology needs to be. But that is a question for another day!

Thanks,

Roger

Kevin Richards wrote:

My only thought is that it seems a bit like a hack and may be too
restrictive when trying to categorise classes.  Ie it looks like you
intend to have ALL RDF classes under the namespace
http://rs.tdwg.org/ontology/ (correct me if I am wrong).  This will
result in a huge list of classes at the one level, and hence, again
diminishing the human readability of the ontology.  I wouldnt know, but
it sounds like it also might cause ontology management headaches later
on?

Kevin

Roger Hyam <roger@tdwg.org> 09/26/06 8:49 PM >>>


Hi Everyone,

In the not very comforting words of software vendors these are "known 
issues" and will be resolved in the next release ;)

But seriously.The namespaces in the TCS names vocabulary do not resolve 
because we didn't have a policy at that time. The use if entity 
references was 'borrowed' from an example (probably Protege output) and 
I wouldn't mind doing away with it.

I have been thinking long and hard about the namespace issues in the 
last few weeks and believe I have a solution that I will propose at TDWG

St Louis. It would be good to have face to face discussions about it and

make a decision there.

To briefly summarize: The issue is getting a namespace convention that 
will work across technologies. Suppose we want to serve data in a 
technology that "isn't very good at namespaces". As an example - if we 
were to have separate namespaces for TaxonNames, TaxonConcepts, 
Specimens, Metadata, GeospatialStuff, Collections and we wanted to 
validate a document using XML Schema that contained all these things it 
would require 6 independent schemas each with it's own target namespace.

If you have ever tried to debug something like this you will know what 
total madness it is. We can't just abandon XML Schema because it would 
rule out not only our existing technologies but GML and probably 
others... It may also be desirable to express our ontology in things 
that aren't even XML.

The only solution I can think is that for the TDWG Ontology we should 
have a single formal namespace of: http://rs.tdwg.org/ontology/

Within the ontology we have a convention for concepts that goes like
this.

A class would be: http://rs.tdwg.org/ontology/tdwg123_MyClass

where 123 is the internal id of the class and MyClass is the class name

A property in MyClass would be: 
http://rs.tdwg.org/ontology/tdwg123_myProperty

where 123 is the *class* id not the property id and myProperty is the 
property name.

An instance would be http://rs.tdwg.org/ontology/tdwg123_789

where 123 is the *class* id and 789 is the instance id (there is nothing

stable about an instance that we could use as an identifier unless we 
force a label property and make it immutable).

In a way this is using the part before the _ as a pseudo namespace.

I think this hits the balance between something that is technology 
independent and something that will produce reasonably human readable 
documents.

It is radical which is why I thought it would be good to talk about it.

Any one got an alternative?

We have to have a solution for this by the end of the St Louis meeting 
as it is critical path for ontology work.

Most grateful for you patience and any thoughts you have.

Roger


Sally Hinchcliffe wrote:

Hi Steve /all

We took that syntax straight from Roger's RDF/TCS examples. I think 
Roger was going to do more work on tidying up those sorts of loose 
ends. I have to admit that my knowledge of RDF and particularly RDFS 
is pretty superficial

We can switch to either the shorter format or the safer fully 
qualified URI - what do people think would be better?

Sally

By the way, the IPNI example you cite has an error:

<tn:nomenclaturalCode rdf:resource="&tn;#botanical" />

Many RDF/XML parsers will see &tn; as an entity which cannot be 
resolved.  Since I don't have a copy of the ontology (and 
http://tdwg.org/2006/03/12/TaxonNames does not resolve), I can only

take

a guess that it should look something like:

<tn:nomenclaturalCode rdf:resource="tn:botanical" />

However, using XML namespace prefixes in resource references inside 
RDF/XML documents tends to cause problems because not all RDF/XML 
parsers are smart enough to dereference the namespace prefix and

build a

fully-qualified resource URI.  A safer form of the above would be the

fully qualified resource URI which looks like:

<tn:nomenclaturalCode

rdf:resource="http://tdwg.org/2006/03/12/TaxonNames/botanical" />

-Steve

*** Sally Hinchcliffe
*** Computer section, Royal Botanic Gardens, Kew
*** tel: +44 (0)20 8332 5708
*** S.Hinchcliffe@rbgkew.org.uk


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-------------------------------------
 Roger Hyam
 Technical Architect
 Taxonomic Databases Working Group
-------------------------------------
 http://www.tdwg.org
 roger@tdwg.org
 +44 1578 722782
-------------------------------------