XML in a Nutshell, 3rd Edition

Schema Basics

This section will construct, step-by-step, a simple schema document representing a typical address book entry, introducing different features of the XML Schema language as needed. Example 17-1 shows a very simple, well-formed XML document.

Example 17-1. addressdoc.xml

<?xml version="1.0"?>
<fullName>Scott Means</fullName>

Assuming that the fullName element can only contain a simple string value, the schema for this document would look like Example 17-2.

Example 17-2. address-schema.xsd

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="fullName" type="xs:string"/>
</xs:schema>

It is also common to associate the sample instance document explicitly with the schema document. Since the fullName element is not in any namespace, the xsi:noNamespaceSchemaLocation attribute is used, as shown in Example 17-3.

Example 17-3. addressdoc.xml with schema reference

<?xml version="1.0"?>
<fullName xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation="address-schema.xsd">Scott Means</fullName>

Validating the simple document against its schema requires a validating XML parser that supports schemas such as the open source Xerces parser from the Apache XML Project (http://xml.apache.org/xerces2-j/ ). This is written in Java and includes a command-line program called dom.Writer that can be used to validate addressdoc.xml, like this:

% java dom.Writer -V -S addressdoc.xml

Since the document is valid, dom.Writer will simply ...