Re: [xml-dev] XQuery & Several records (instead of one xml-field)

[Jim Melton <jim.melton@acm.org>]

Liam,

In point of fact, Oracle's server-based XQuery engine (distinguished 
from our middle-ware or client-based XQuery engines) compiles XQuery 
code into the same underlying execution tree structure into which the 
SQL engine compiles SQL code.  Therefore, our XML data handling is 
fully integrated with handling of traditional relational 
data.  Obviously, we think that is the right approach for our 
users.  And, equally obviously, IBM thought that having a separate 
engine that is bound in some way to the relational engine was a 
preferred approach.  Probably we're both right ;^)

Hope this helps,
    Jim

At 10/18/2007 10:54 PM, Liam Quin wrote:
>On Fri, Oct 19, 2007 at 09:12:46AM +0530, Mukul Gandhi wrote:
>[...]
> > Suppose, that a RDBMS table is defined like following:
> >
> > Table: X
> > col1 - number (10),
> > col2 - varchar2 (15),
> > col3 - XMLType
> >
> > The column "col3" is of type XMLType (this is just illustrating the
> > concept, and does not follow a syntax of a product or a standard).
> >
> > Now the XQuery program (the XQuery engine is probably embedded in the
> > RDBMS) can query the column "col3". Something like:
> >
> > xquery db-func:XML-column('X.col3')/root/a/b/c
>
>Right.
>
> > Now my questions are
> > 1) It is probably possible for a XQuery engine to reuse it's design
> > (i.e. for the XML infoset/PSVI) to construct a data model instance
> > from the XMLType column. Do most of the XQuery engines embedded in the
> > RDBMS work this way?
>
>The Xpath 2.0 and XQuery 1.0 Data Model is conceptual.  That is, the
>database doesn't actually have to construct anything at all, as long
>is it generates the right results.
>
>However, if you have specified that the column contains XML, and asked
>for it to be indexed, it's likely that no pointy-bracket parsing will
>be needed at runtime for many queries.
>
>DB2 at least have released a white paper showing that their XQuery
>implementation accesses the underlying data store and does not need
>to go through the SQL engine; I believe the same is true for Oracle,
>and possibly also Microsoft SQL Server.
>
> > 2) Supposing a RDBMS table is defined like this (a very simple
> > traditional definition):
> > Table: X
> > col1 - number (10),
> > col2 - varchar2 (15),
> > col3 - float
> >
> > Can a XQuery engine work on this table structure?
>Yes.
>
>That is, some can and some can't, and some do it via SQL and
>JDBC or ODBC, and some perhaps more efficiently.
>
>Liam
>
>--
>Liam Quin, W3C XML Activity Lead, http://www.w3.org/People/Quin/
>http://www.holoweb.net/~liam/ * http://www.fromoldbooks.org/
>W3C participant/staff contact for the W3C XML Query Working Group
>
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========================================================================
Jim Melton --- Editor of ISO/IEC 9075-* (SQL)     Phone: +1.801.942.0144
   Co-Chair, W3C XML Query WG; XQX (etc.) editor    Fax : +1.801.942.3345
Oracle Corporation        Oracle Email: jim dot melton at oracle dot com
1930 Viscounti Drive      Standards email: jim dot melton at acm dot org
Sandy, UT 84093-1063 USA          Personal email: jim at melton dot name
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=  Facts are facts.   But any opinions expressed are the opinions      =
=  only of myself and may or may not reflect the opinions of anybody   =
=  else with whom I may or may not have discussed the issues at hand.  =
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