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Re: Innovation, community and queries

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Mon, 03 Jun 2002 13:13:37 +0300
To: ext Arnold deVos <adv@langdale.com.au>, Danny Ayers <danny666@virgilio.it>, Uche Ogbuji <uche.ogbuji@fourthought.com>
CC: "Seaborne, Andy" <Andy_Seaborne@hplb.hpl.hp.com>, "ext Thomas B. Passin" <tpassin@comcast.net>, RDF Interest <www-rdf-interest@w3.org>
Message-ID: <B9211C01.15F75%patrick.stickler@nokia.com>

On 2002-06-01 9:25, "ext Arnold deVos" <adv@langdale.com.au> wrote:

> If anyone is interested in some fairly complete draft proposals for RDF
> query languages that are expressed.in RDF I have two:

Thanks for the pointers. Some comments...

> [1]  http://www.langdale.com.au/RDF/NexusQueryLanguage.pdf

This seems more like query in XML than in RDF. Perhaps I missed something.
The template priority looks interesting. Examples of its use in practice
would be nice to see.

> [2] http://www.langdale.com.au/RDF/DAML-Query.html

This is clearly RDF query in RDF (well DAML ;-)

I find the partitioning of the query into the select and from portions
a bit cumbersome -- in the same way that trying to view an XML instance
stored in an RDBMS is cumbersome. You have to kinda keep track of
the target description on several levels -- first specify the properties
of relevance in the select statements and then describe, be means of
a class no less, the actual value constraints for those properties.

And don't the property restrictions make the property select statements
redundant?

I think that the average RDF user (or even the average advanced RDF
but not DAML user) will not warm too much to such a representation.

Still, DAML die-hards may feel right at home with it ;-)

> [3] http://uche.ogbuji.net/tech/rdf/versa

This last link is broken, unfortunately.

Cheers,

Patrick

> 
> - Arnold
> 
> Arnold deVos
> Langdale Consultants
> http://www.langdale.com.au
> 
> 
> 
> 
> ----- Original Message -----
> From: "Danny Ayers" <danny666@virgilio.it>
> To: "Uche Ogbuji" <uche.ogbuji@fourthought.com>
> Cc: "Seaborne, Andy" <Andy_Seaborne@hplb.hpl.hp.com>; "'Patrick Stickler'"
> <patrick.stickler@nokia.com>; "ext Thomas B. Passin" <tpassin@comcast.net>;
> "RDF Interest" <www-rdf-interest@w3.org>
> Sent: Saturday, June 01, 2002 8:57 AM
> Subject: RE: Innovation, community and queries
> 
> 
>> 
>> 
>>>>> properties(@"x:spam")
>>>>> @"x:spam" - properties() -> *
>>>> 
>>>> Another good reason for an RDF QL in RDF!
>>> 
>>> Possibly.  It's hard to judge without seeing your proposal for
>>> expressing it
>>> in RDF instead.
>> 
>> Fair response, and no, as you probably guessed, I don't have a proposal at
>> hand.
>> 
>>> Of course, I must warn you I'm a sceptic.
>> 
>> Me too, which is partly why I have a knee-jerk reaction to new syntaxes.
>> 
>>>> Seriously though, I do think such a QL would be extremely
>>> useful, not only
>>>> because it would generally help interop.  It would also mean that a
> whole
>>>> range of common expressions could become easier in RDF (without having
> to
>>>> drop into DAML-land),
>>> 
>>> Examples?
>> 
>> Essentially the kind of stuff like that which SQL scores on (almost
>> irrespective of the relational model) - e.g. forall kind of things.
>> 
>>>> and also make things like XSLT-ish transformations a
>>>> lot more straightforward.
>>> 
>>> We do this in 4Suite by using Versa to query and using XSLT itself
>>> to generate
>>> transformed RDF/XML.  Works well, but we plan to come up with an
>>> XUpdate-like
>>> syntax as well.
>> 
>> Hmm - I've experimented in the RDF+XSLT area myself, but have serious
> doubts
>> on its potential - ok, it can probably solve a lot of specific problems,
> but
>> having to think in trees is a bit ugly for the general case.
>> 
>>> I'm not sure how Query in RDF would help make this more palatable
>>> than me.
>>> After all, the analog of RDF query in XSLT, XPath, is not in XML
>>> syntax.  It
>>> still works quite well.
>> 
>> Very true, but might it just be that with the DOM model doesn't need to be
>> good at metamodelling, which is something I would hope RDF languages would
>> be good at.
>> 
>>>> Not unrelated to the interop point, the ability to
>>>> save sets of queries in a common format like RDF/XML has to be a
>>> plus - same
>>>> parser etc etc.
>>> 
>>> This is a trivial matter of writing an RDF binding for whatever
>>> data model a
>>> QL uses.
>> 
>> Writing a binding is trivial, writing a good binding is another matter.
>> 
>> Cheers,
>> Danny.
>> 
>> 
> 
> 
> 
> 

--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Monday, 3 June 2002 06:14:41 GMT

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