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Note that the XSD file has to be accessible through HTTP. In the example,
file:///C:/temp/TestSchema.xsd is a true URL pointing to a location. Namespaces
such as http://www.ibm.com, on the other hand, just use the URI notation to be
globally unique. Assuming that noProtocol://www.ibm.com is globally unique, it
would be a valid namespace name as well.
The syntax of the schema location attribute defined by XML standards is:
xsi:schemaLocation="targetnamespaceURI locationURI">
This is a quite tricky notation because it is not obvious that two different entities
with a similar syntax but different semantics appear in the same attribute. Even
worse, the locationURI is often not a full network address, but a simple local file
name.
Target namespace
Several of the XSD elements introduced above can define a target namespace,
which is either absent or a namespace name.
The target namespace serves to identify the namespace within which the
association between the element and its name exists. In the case of declarations,
this association determines the namespace of the elements in XML files
conforming to the schema. An XML file importing a schema must reference its
target namespace in the schemaLocation attribute. Any mismatches between the
target and the actual namespace of an element are reported as schema
validation errors.
In our example, the target namespace is http://www.ibm.com; it is defined in the
XSD file and referenced twice in the XML file. Any mismatch between these three
occurrences of the namespace lead to validation errors.
10.1.7 Schema and style using XSLT and XSL
The extensible style language (XSL) is a language defined by the W3C for
expressing style sheets. It has three parts:
► XSL transformations (XSLT), which is used for transforming XML documents.
► The XML path language (XPath), which is a language used to access or refer
to parts of an XML document.
► XSL-FO, which is a vocabulary for specifying formatting semantics.
A transformation in XSLT must be a well-formed document and must conform to
the namespaces in XML, which can contain elements that may or may not be
318 IBM WebSphere Application Server - Express V5.0.2 Developer Handbook