XQuery from the Experts: A Guide to the W3C XML Query Language

What Is XML Data?

XML data can be understood at two levels: the textual representation, and the model of this data as a tree of nodes.

XML as Text

XML is often seen in its textual form. As text, XML may be viewed in any text editor and easily passed around the World Wide Web using text-based protocols such as HTTP. The example below shows some XML text. Note the tags Person and FirstName. Such tags give names to the data.

<?xml version="1.0"?>
<Person id="12">
   <FirstName>John</FirstName>
   <LastName>Smith</LastName>
<Person>

XML Data Model

In a rough sense, the XML data model (XML Infoset [INFOSET]) describes XML as a tree of data. The XQuery data model is essentially this same tree definition with some important additions, such as sequences ...