XML in a Nutshell, 3rd Edition

Empty Elements

In many cases, it is useful to declare an element that cannot contain anything. Most of these elements convey all of their information via attributes or simply by their position in relation to other elements (e.g., the br element from XHTML).Let’s add a contact-information element to the address element that will be used to contain a list of ways to contact a person. Example 17-8 shows the sample instance document after adding the new contacts element and a sample phone entry.

Example 17-8. addressdoc.xml with contact element

<?xml version="1.0"?>
<addr:address xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://namespaces.oreilly.com/xmlnut/address 
      address-schema.xsd"
    xmlns:addr="http://namespaces.oreilly.com/xmlnut/address"
    addr:language="en">
  <addr:fullName>
    <addr:first>William</addr:first>
    <addr:middle>Scott</addr:middle>
    <addr:last>Means</addr:last>
  </addr:fullName>
  <addr:contacts>
    <addr:phone addr:number="888.737.1752"/>
  </addr:contacts>
</addr:address>

Supporting this new content requires further modifications to the schema document. Although it would be possible to declare the new element inline within the existing address-element declaration, for clarity it makes sense to create a new global type and reference it by name:

<xs:element name="address"> <xs:complexType> <xs:sequence> <xs:element name="fullName"> . . . </xs:element> <xs:element name="contacts" type="addr:contactsType" minOccurs="0"/> </xs:sequence> <xs:attributeGroup ...