Databases Reference
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frameworks such as Ruby on Rails or Zend Framework to build Web
applications that leverage persistent XML store in DB2.
Will you need to generate XML from relational data or vice versa?
Your application can leverage XML constructor functions to build XML from
relational data before applications can process it. In contrast, some use cases
require XML data to be shredded into relation columns before the data can be
accessed by an existing application.
How often will XML documents be accessed, updated, and manipulated? Will
you need to update fragments or the whole document?
Choosing the right query and interface model depends on whether an
application is read only or both read and update. XQuery can limit your
application to read only, so you need to carefully decide if full document
update is reasonable.
Will you need to transform the XML to HTML, WML, or other languages, and
how will your application transform the XML?
If your application needs to be accessed by different clients, XSLT may be
used to transform. While storing data in pureXML, you can make sure the
structure complies with the specific XML schema.
2.2.3 DB2 hybrid query engine
DB2 hybrid engine processes SQL or XML and XQuery queries in an integrated
manner. DB2 unifies XML storage, indexing, and query processing with existing
relational storage, indexing, and query processing. DB2 also provides an XML
schema repository (XSR) to register and maintain XML schemas and uses those
schemas to validate XML documents. The DB2 utilities such as IMPORT and
EXPORT have been enhanced to support XML data and the new graphical
XQuery builder lets you construct XQueries.
The hybrid engine allows existing client applications to access DB2 data through
relational APIs, yet it offers new SQL or XML APIs to publish relational data in
XML format and full document retrieval from pureXML storage. Additionally, the
new SQL or XML querying functions provide SQL applications with subdocument
level search and extract capabilities by embedding XQuery statements into SQL
statements.
An XML application can interact with the DB2 server via the XML interface by
using the XQuery language, which is supported as an stand-alone query
language independent of SQL. XQueries can optionally contain SQL statements
to combine and correlate XML data with relational data. A client application can
benefit immensely from this integration of the two languages supported by DB2.
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