Datasheet

A browser uses the XML DOM to build a picture of an XML document, as shown in Figure 1-3. The browser
contains a parser that does not care what the data is, but rather how data is constructed. In other words,
the DOM contains a multiple dimensional (hierarchical) array structure. That array structure allows access
to all tags and all data, without the programmer having to know the contents of the tags within it and
even the names of the tags. An XML document is just data and so any data can be contained within it.
When creating weather reports for people in different parts of the world, the underlying templates that
make the web pages look nice are all exactly the same; only the data is different. This is where this
book comes into being. Data stored in databases as traditional relation tables can be used to create
XML documents that can also be stored in a database. The XML DOM allows programmatic access
into XML documents stored in a database. In other words, you can create XML documents, stuff them in
a database, and then use database software to access the documents either as a whole or in part using
the XML DOM.
That is really what this book is about. It is, however, necessary to explain certain facets of XML before
we get to the meat of databases and XML. You need to have a basic picture of things such as XML and
XSL first.
XML Browsers and Different
Internet Browsers
There are varying degrees of support for XML in different Internet browsers. In general the latest ver-
sions of Internet Explorer or Netscape will do nicely. Using an older version of a software tool can
sometimes be asking for trouble.
Using a non-mainstream browser might also be limited in scope but this is unlikely if you use the latest
version. There are, however, some very specific technologies used by specific vendors. Microsoft’s Internet
Explorer falls into this category. Then again, Internet Explorer is probably now the most widely used
browser. So, for browser-based examples, I’ve used Microsoft technology.
Database technology being used in this book will primarily be Oracle Database from Oracle Corporation
and SQL-Server Database from Microsoft. Once again, bear in mind that the focus of this book is on
using XML as a database, or in other databases.
The Document Type Definition
The Document Type Definition (DTD) is a method of defining consistent structure across all XML docu-
ments within a company, an installation, and so on. In other words, it allows validation of XML documents,
ensuring that standards are adhered to even for XML data where the source of the XML data is external
to the company.
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