IVOA Vocabularies - WD

[Norman Gray]

Greetings.

On 2007 Sep 5, at 14:40, Andrea Preite Martinez wrote:

> the WD document "IVOA Vocabularies" v1.01 is now available at
> http://ivoa.net/Documents/latest/VOcabularies.html

>> Comments are welcome!

I am completely baffled.

The following are a few brief comments, though I echo Tony, Kjetil  
and Brian's.

I appreciate the problem -- there are multiple astrophysical  
vocabularies, as the document vividly points out.  I fail to  
appreciate how adding a new vocabulary plus _two_ (count them) new  
syntaxes addresses this.



Doug remarked:

> Since there are multiple such standards,

No, there's only one, RDF, plus a couple of standardised overlays.

> they can be complex,

RDF is about as complex as a brick.

> and they keep evolving

As Brian pointed out, RDF was standardised before XML Schemas (2004,  
as the second edition of a 1999 W3C Rec), finalising a standard which  
was effectively complete a decade ago[1], building on probably a  
decade before _that_ of clever people thinking hard and prototyping  
busily about the best way to approach this problem.  And getting it  
right.

> One should also keep in mind that we might want to read this  
> information
> into astronomy client applications which just want the basic  
> vocabulary,
> do not need advanced inference capabilities, etc., and do not want to
> be dependent upon some complex semantic web technology.

If apps want to read, write and get value from RDF, with or without  
inferencing, they can do so _today_ using industrial strength tools 
[2]; if they want to read VOcabularies, they've got to wait for  
someone to write, debug and port tools from scratch.



I and others have worn ourselves out trying to introduce RDF to the  
VO (an area which is a more natural beneficiary of the RDF approach  
than many areas which have applied it successfully).  I've tried  
saying it's simple, and that it's sophisticated; I've tried saying  
it's new, and that it's old; I've tried saying it's got pointy  
brackets (just like XML, folks), and that it's readable; I've tried  
using the word 'reasoning', and scrupulously avoiding it; I've tried  
giving high-level arguments, and I have even tried, heaven help me,  
showing running code; and ... nothing, no response, not even much in  
the way of rebuttals, online or off.  No, the VO just carries on  
inventing its own private syntaxes.  What is it I'm doing wrong?

Yes, the VO is technologically very conservative, for intelligible  
reasons, but we're really very far behind the curve here.  The STP  
folk are getting benefit from this (hello, Peter), it's widely used  
in industry back-office applications, and the big RDF poster child is  
bioinformatics.  Yes -- we've been out-technologised by the biologists.

----

For what it's worth here's how I would address the problem of  
multiple vocabularies:

   1. For each of the vocabularies listed in the VOcabulary document,  
describe a mechanical mapping from terms to URLs.  Use the resulting  
strings as the interoperable labels (possibly compacted, if you want,  
using namespace prefixes).

   2. Use RDFS to annotate these strings nonexhaustively with  
descriptions, aliases, and equivalences in other vocabularies.

   3. Use standard libraries, in the language and on the platform of  
your choice, to build on the result.

   4. There is no step 4.

This covers both the multiple vocabularies and the 'SV token  
grammar'.  The only thing this would have difficulty with is 'NOT',  
because it's well known that the concept 'not(X)' is hard to discuss  
meaningfully in this context.  If you don't like that, then there are  
other thoroughly shaken-down syntaxes from the last few decades of  
computing which could be adapted to the purpose.



I like Kjetil's `crossing the stream for water'.  But this is the VO  
crossing the warm, fast-flowing, biodiverse Amazon for water.

Best wishes,

Norman


[1] http://www.w3.org/TR/WD-rdf-syntax-971002/
[2] There's a ridiculously large number of tools, parsers and more at  
<http://esw.w3.org/topic/SemanticWebTools>, of which there are a few  
things that `everyone uses' (except us, of course).

-- 
------------------------------------------------------------
Norman Gray  :  http://nxg.me.uk
eurovotech.org  :  University of Leicester, UK