7.1. A Simple XML Schema Document Example

Listing 7.1 is a trivial XML schema document that specifies only an element type whose structure type is the built-in string datatype.

Listing 7.1. A Trivial XML Schema Document (simpleSchema.xsd)

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> 
    <xsd:element name="stringElement" type="xsd:string"/> 
</xsd:schema> 

A few features to point out about the preceding trivial schema:

• The only attribute of the schema element—xmlns:xsd—specifies the namespace http://www.w3.org/2001/XMLSchema. Furthermore, the xmlns:xsd attribute specifies the corresponding namespace prefix, ‘xsd’. The specification of the XML schema namespace implies a corresponding XML schema document XMLSchema.xsd, which is the Schema for Schemas.

• xmlns:xsd is not a schema attribute per se; the xmlns:xsd attribute applies to any XML element.

• There is explicitly no target namespace. Note that in the subsequent example, a namespace prefix does not precede the element name ‘tokenElement’.

Given the XML schema document in Listing 7.1, the following is a valid XML instance:

<stringElement 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation= 
   "http://www.XMLSchemaReference.com/examples/Ch07/notation.xsd 
>A String Value</stringElement> 

Note that there is exactly one element in the XML instance: a stringElement. The value of that stringElement is ‘A String Value’.