Database Reference
In-Depth Information
▪ Responsive full-text searches.
▪ Features that are familiar from working with relational databases, such as joins across doc-
ument collections, user-defined functions, search support for metadata as well as data, and
more.
▪ Flexible use of XML throughout the stack, such as when using XForms in the presentation
tier.
▪ Other features, such as storage of non-XML documents (for example, full plain-text [un-
structured] documents).
If you're not familiar with XPath as a means to find data in an XML document, consider the
following example XML document:
<catalog>
<plays>
<play name='Hamlet'><price>5.95</price></play>
<play name='King Lear'><price>6.95</price></play>
</plays>
</catalog>
Given this XML document, the following XPath expression will give us the value “6.95”, which
is the result of navigating to the value of the
price
element inside the
play
element whose value
for the name attribute is “King Lear”:
//catalog/plays/play/[@name='King Lear']/price
There are a variety of XML databases in open source projects and commercial offerings. They
typically employ one of two data storage mechanisms: text-based or model-based. Text-based
XML databases typically will store their data as large text files, character large objects (CLOBs),
or even as a binary large object (BLOB) in an underlying relational database, performing the
translation for you. Model-based XML databases don't directly store the text of the XML docu-
ment; instead, they parse documents into an internal proprietary object model that appears to the
developer as an XML document. Often this boils down to breaking down the various parts of
an XML document (elements, attributes, etc.) and storing them as fragments within a relational
database.
The following sections offer a quick overview of some of the popular XML databases.
SoftwareAG Tamino
Tamino was one of the earliest XML-native databases. It's a mature commercial offering that
supports a wide variety of the kinds of functions you'd expect in an “enterprise-ready” database,
such as high availability.
