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Re: Proposed XQuery requirement and/or objective

From: Jim Hendler <hendler@cs.umd.edu>
Date: Thu, 15 Jul 2004 16:29:21 -0400
Message-Id: <p06110400bd1c94ebefa9@[10.0.0.11]>
To: "Jeff Pollock" <Jeff.Pollock@networkinference.com>, <public-rdf-dawg@w3.org>
At 11:24 -0700 7/15/04, Jeff Pollock wrote:
All-

As everyone in attendance at the DAWG FTF is aware, the Network 
Inference position is that XQuery represents an ideal concrete syntax 
to facilitate more widespread and rapid adoption of the semantic web 
stack, beyond just RDF.

In support of the charter, NI proposes that the discussion of a 
strawman query language is not inherently at odds with an eventual 
XQuery based concrete syntax. The DAWG charter contemplates three 
stages of specification evolution; (1) strawman language, (2) 
abstract syntax and (3) concrete syntax. Network Inference does not 
perceive BRQL, RDQL, or N3QL proposals as necessarily excluding an 
eventual outcome that is consistent with an XQuery concrete syntax. 
The DAWG charter also clearly states that: "The RDF DAWG should aim 
to maximize W3C technology re-use, while also taking account of 
differences between the RDF graph data model and the XQuery data 
model" - thereby supporting our objective that XQuery be an integral 
part of an end-user's interface with the eventual DAWG language 
recommendation.

Therefore, NI proposes that a new requirement be considered by this group:

"The query language shall have an XQuery compatible concrete language syntax."

Network Inference has formalized the rationale for this requirement 
in the attached document that explores the facets of why this is 
important to us, and ultimately as to why it should be important to 
the W3C community at large.

Comments, stones, or support are welcome.

Kind Regards,

-Jeff-



Jeff - thanks for this document - it seems helpful - since I'm not 
there I cannot really follow the arguments, but I must admit I find 
this document confuses me more, not less.

some questions;
  you say 20+ vendors support some sort of Xquery.  best I can tell, 
however, most of those assume you are using a XML DB.   Some 200+ 
vendors seems to support SQL, including MS access and Oracle and lots 
of the other "big kids" -- and they don't assume an XML DB.
  I'm assuming that in most of the applications people will build, the 
RDF will live in a triple store (like Tucana builds, for example) and 
thus they won't be in an XML DB per se -- so would Xquery really 
speed up adoption or slow it down?  SQL is also taught in every CS 
dept in America (I can't speak for outside the US, although I did sit 
in on some DB lectures using SQL in the UK, so it's at least taught 
there as well).  There are also many packages (like JDBC) that 
provide APIs for working with SQL-like langauges, wouldn't that be an 
argument for that sort of syntax?

You show RDFS/OWL/Rule query langauges as somehow being more easy in 
Xquery, but again I think that is because you are assuming these 
things will be kept in their RDF/XML documents, or in APIs that 
respect the "boundaries" of those.  I already see many applications 
moving towards multiontologies w/linking, and that seems to me to 
argue that we simply don't know yet which of these models are better.

Let me be clear, I'm not opposed to an XQuery-based model, and I am 
not really a big fan of SQL, but I see a lot of the DB community 
folks (Several papers at TODS and VLDB workshops, in fact) that are 
arguing in favor of RDF DBs precisely because they can handle 
algebras similar to relational, and because they can scale well in 
the way RDBMS do (and they're worried about the scaling of XML DBs, 
esp in the VLDB world)

So I would be okay with the requirement you propose assuming
  one - this can't be the ONLY concrete language syntax - I would 
expect that we could do something like we did in the OWL case, where 
we had an abstract syntax with two surface realizations (XML and 
RDF/XML) - this guaranteed that interoperability between the XML and 
RDF version was possible, as they were provably mappable one to the 
other
  two - I would like to see some evidence of the scalability of these 
Xquery things -- this is not meant to be hostile, I'm just a lot more 
comfortable with the SQL world (where I have over 25 years of 
experience) than with the newer Xquery world, so I simply don't know 
what Xquery Algebras and calculi look like, and thus I don't have an 
inuitive feel for their scalability, etc.    I suspect Tucana and 
others would be willing to make their DB query times public for some 
set of queries - is there any way we could run a comparison on some 
large scale test cases or someting like that (I looked on the NI site 
for some examples, but there is nothing publicly available)

Please, let me be clear -- rereading this it looks like I'm being 
negative, but I don't mean to be -- I'm actually trying to understand 
the situation and see whether the positions we seem to hold are 
compatible or not -- I certainly have not predecided this issue
  -JH
p.s. And if you think I may be somehow hostile to NI, please talk to 
Jack Berkowitz and get him to tell you how supportive I was during 
the Web Ont work.
-- 
Professor James Hendler			  http://www.cs.umd.edu/users/hendler 
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  240-277-3388 (Cell)
Received on Thursday, 15 July 2004 16:29:56 GMT

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