xpath to sql translation

[Terry P]

Are there any tools (java classes, tag libraries) which can translate
xpath statements into a SQL query?

Given an xpath query which has a predicate that filters node values or
attributes, I want help constructing the Where clause of a SQL
statement that will mirror the expressions and functions contained in
the predicate.

Such a tool may require an XML to DB mapping or it would need to make
assumptions about the structure of the document and the tables.

Thanks for any advice.

Terry

 

[Tjerk Wolterink]

Are there any tools (java classes, tag libraries) which can translate
xpath statements into a SQL query?

Given an xpath query which has a predicate that filters node values or
attributes, I want help constructing the Where clause of a SQL
statement that will mirror the expressions and functions contained in
the predicate.

Such a tool may require an XML to DB mapping or it would need to make
assumptions about the structure of the document and the tables.

Thanks for any advice.

Terry

What sory of database are you talking about?
A ordinary relational database? Or an XML-database.
Xml-databases are new and not very fast, but there is extensive research in xml-database-system.
Those system support xpath and xquery as query languages.

I'f you want to map xpath onto sql, then your're right: you need some
rules about how xml is mapped onto the relational database.
With those rules you could map xpath expression to sql expressions.

I don't know wether they exists. I myself have my own mapping rules,
rather simplistic rules but it does the job for me.

 

[Jeff Kish]

What sory of database are you talking about?
A ordinary relational database? Or an XML-database.
Xml-databases are new and not very fast, but there is extensive research in xml-database-system.
Those system support xpath and xquery as query languages.

I'f you want to map xpath onto sql, then your're right: you need some
rules about how xml is mapped onto the relational database.
With those rules you could map xpath expression to sql expressions.

I don't know wether they exists. I myself have my own mapping rules,
rather simplistic rules but it does the job for me.

I was under the (mistaken?) assumption that eventually xpath will let you
query multiple data sources, i.e. databases included.

Is this true?
Jeff Kish

 

[Tjerk Wolterink]

I was under the (mistaken?) assumption that eventually xpath will let you
query multiple data sources, i.e. databases included.

Is this true?
Jeff Kish

XPath is a language to query xml documents, or multiple xml documents, it returns a node-set.
It cannot query ordinary relational based databases, i think.

But you can query multiple data-sources [multiple xml files, using the document() function].
And maybe in the future you can also query XML-based databases with XPath,

But xpath is a rather simple query language for xml, XQuery is much more powerfull.

 

[David Carlisle]

But xpath is a rather simple query language for xml, XQuery is much
more powerfull.

Xquery is a superset of Xpath 2 but the extra features are mainly
related to element construction rather than querying.


David

 

[Terry P]

Tjerk,
Thanks for the response.
In particular, I expect to be using a DB2 database with XML Extenders
(IBM). I may need this on different platforms - Linux, ISeries,
Win2000.

A Java/SQL solution may be best. I am hoping for something like a
Java class that can parse the XPath and create the Where clause of a
SQL query. Special SQL functions might be used to emulate the
standard XPath functions.

XPath has been around for a while, so I am surprised that I have not
been able to find "off the shelf" tools to do this.

Terry

 

[Jeff Kish]

Tjerk,
Thanks for the response.
In particular, I expect to be using a DB2 database with XML Extenders
(IBM). I may need this on different platforms - Linux, ISeries,
Win2000.

A Java/SQL solution may be best. I am hoping for something like a
Java class that can parse the XPath and create the Where clause of a
SQL query. Special SQL functions might be used to emulate the
standard XPath functions.

XPath has been around for a while, so I am surprised that I have not
been able to find "off the shelf" tools to do this.

<snip>
If you go to http://xquery.com/ you see this blurb:

"what is xquery?"
"XQuery is a technology under development by the World Wide Web Consortium
(W3C) that's designed to query collections of XML data -- not just XML files,
but anything that can appear as XML, including relationtional databases.
XQuery has broad support from IBM, Microsoft, and Oracle as well as
application server vendors such as BEA and Software AB."

I may of misquoted, and this may be accurate or not I don't know. It is by
Jason Hunter who I believe has a good reputation in these matters.

HTH


Jeff Kish

 

[Tjerk Wolterink]

Tjerk,
Thanks for the response.
In particular, I expect to be using a DB2 database with XML Extenders
(IBM). I may need this on different platforms - Linux, ISeries,
Win2000.

A Java/SQL solution may be best. I am hoping for something like a
Java class that can parse the XPath and create the Where clause of a
SQL query. Special SQL functions might be used to emulate the
standard XPath functions.

XPath has been around for a while, so I am surprised that I have not
been able to find "off the shelf" tools to do this.

Terry

I've never seen an Xpath to SELECT [] FROM [] WHERE clause translation.
And it is not easy to do that,
because you have to have rules in how you store xml in a relational database.

I think that's also the reason there are no tools to do that.
So can't help you there.

 

[Terry P]

Tjerk,

We have found a couple of products on IBM's Alphaworks site. One of
them uses the "DB2 XML Extenders" mapping of XML<=>SQL. The other
seems to create a default mapping based on SQL metadata.

Both of them are limited to Linux & Windows. While we may use these,
our main RDB is DB2 for ISeries. So we are still checking.

If you are curious, the links are:
http://www.alphaworks.ibm.com/tech/xtable
http://www.alphaworks.ibm.com/tech/db2uriaccess

Thanks for your help,

Terry

Tjerk,
Thanks for the response.
In particular, I expect to be using a DB2 database with XML Extenders
(IBM). I may need this on different platforms - Linux, ISeries,
Win2000.
....

I've never seen an Xpath to SELECT [] FROM [] WHERE clause translation.
And it is not easy to do that,
because you have to have rules in how you store xml in a relational database.

I think that's also the reason there are no tools to do that.
So can't help you there.