QRE: How do Java Xquery technologies fit ?

[Michael Kay]

First point is that XQJ is an interface - a way that XQuery users can talk
to XQuery implementations. It is not itself an XQuery implementation. XQJ is
to Saxon as SQL is to relational databases.
 
>What I am also wondering is the extent to which products like datadirect
Xquery have utilised the XQJ API to provide easy access to a relational
database and how an XML view of a relational database can be derrived ? 

That's a question very specific to the DataDirect product. 
 
>My only guess at the moment is that it makes an SQL call to retrieve all
the column names and builds some sort of internal schema using this ?

Well, I guess there's a lot more to it than that, but I expect you're along
the right lines.
 
>I'm I right in thinking that the XQJ API alone offers no such automatic
connection to table columns in a non XML relational database.
 
XQJ is just a pipe down which you can send XQuery requests. Unless there's
someone listening at the other end, it can't do anything.
 
>If this is the case my questions is whether Saxon can be modified to do
this (if at all advisable) and what work I would need to do to achieve this.

It's possible in theory but it's a *very* significant amount of work -
especially for someone who isn't already aware that it's a large project.

>I noticed when playing with the evaluation version of DataDirect Xquery
that it loaded what appears to be a saxon module 
 
DataDirect XQuery uses some component technology acquired from Saxonica. It
does a lot more than Saxon (by distributing a query to multiple data sources
and assembling the results), but it reuses some of the Saxon technology to
do parts of the query processing.
 
Michael Kay
Saxonica 

  _____  

From: http://x-query.com/mailman/listinfo/talk [mailto:http://x-query.com/mailman/listinfo/talk] On Behalf
Of paul agbetile
Sent: 20 June 2008 12:15
To: http://x-query.com/mailman/listinfo/talk
Subject:  How do Java Xquery technologies fit ?


Hi, I am about to embark on a project that will require me accessing XML
sources as well as relational databases and would really appreciate some
help in trying to navigate through alot of what has me confused.
 
Firstly I should mention I am new to XQJ and Xquery. I started a few days
ago with Michael Kay's "Learn XQuery in 10 Minutes" tutorial which I found
really helpful and have written a few queries since. 
I am struggling to understand where XQJ ends and products like Saxon and
datadirect Xquery begin. What I am also wondering is the extent to which
products like datadirect Xquery have utilised the XQJ API to provide easy
access to a relational database and how an XML view of a relational database
can be derrived ? 
My only guess at the moment is that it makes an SQL call to retrieve all the
column names and builds some sort of internal schema using this ?
 
I'm I right in thinking that the XQJ API alone offers no such automatic
connection to table columns in a non XML relational database. If this is the
case my questions is whether Saxon can be modified to do this (if at all
advisable) and what work I would need to do to achieve this.
 
At present my assumptions range from having to write my own JDBC driver
(that can generically talk to several databases) as well as devising some
sort of Xquery to SQL translation. I noticed when playing with the
evaluation version of DataDirect Xquery that it loaded what appears to be a
saxon module ? This again has me confused as to how all these technologies
fit in with one another.
 
Thanks,
Paul

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