XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (195 page)
Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
A zero-length string cannot be used as a namespace URI, so a runtime error occurs if the result of the computation just described is a zero-length string.
Note that a namespace node is not the same thing as a namespace declaration. An element has a namespace node for every namespace that is in scope. A namespace undeclaration, such as
xmlns=“”
in XML Namespace 1.0, orxmlns:z=“”, which is allowed by XML Namespaces 1.1, is not represented by a namespace node. Rather, it is represented in the data model by the absence of a namespace node.
Usage and Examples
Although namespace declarations are a special kind of attribute in the surface XML syntax, they are represented quite differently in the XDM data model. This means that you cannot produce namespace declarations in the result document by using
The namespace declarations produced by the serializer are derived from the namespace nodes that are present in the result tree. However, there isn't a one-to-one mapping between namespace nodes and namespace declarations. An element in the result tree has a namespace node for every namespace prefix that is in scope for this element (even if it's also in scope for the element's parent).
In the vast majority of cases, the namespace nodes needed in a result tree are created automatically.
For namespaces used in the names of elements and attributes, this is guaranteed by the namespace fixup process described under
Creating (or not creating) a namespace node will never change the name of an element or attribute. If you are outputting an element with local name The only difficulties arise therefore when you need namespaces to be declared in the result document that are not used in element and attribute names. I've come across three reasons for doing this: 1. 2. 3. In the rest of this section we'll focus on the use of QNames in element and attribute content. An example is if you want to output the following: Your document must then contain a namespace declaration that binds the namespace prefix Here is one convenient way to output the above element: select=“‘http://www.w3.org/2001/XMLSchema’”/> Note that there is no need to use
in no namespace, and you want it to be in namespace
http://garden-furniture.com/ns
, then you need to change the instruction that creates the element node. If you get the element names right (remembering that an element name includes the namespace URI as well as the local part), then the namespace nodes will usually look after themselves.
You want the namespace to be declared once on an outer element of the document, whereas in the normal course of events it would be declared many times on inner elements. This is essentially cosmetic, but it can make a significant difference to the readability (and the size) of your output. In some cases this kind of declaration is necessary to make the output valid against a DTD, or simply against a written specification—the Locale Data Markup Language, for example, requires the element
Your document uses namespace prefixes in the content (as distinct from in the names) of elements and attributes. This is the most common case and we'll devote the rest of the section to it.
The definition of the result document type uses namespace declarations as some kind of marker, where the mere presence of the namespace declaration carries information, whether or not the prefix that's being declared is ever used. This is a pretty weird way of using namespaces, but there's no law against it. In the case I saw, it was done because adding namespace declarations to a document can be done without changing the schema.xsto the namespace URIhttp://www.w3.org/2001/XMLSchema. The serializer will only produce such a declaration if it encounters a namespace node in the result tree that binds this prefix to this URI.xsito the namespace
http://www.w3.org/2001/XMLSchema-instance
. Because this namespace is used in an attribute name, the namespace fixup process will ensure that it is declared. In fact, it would be declared in this case even without namespace fixup, because the rules for a literal result element ensure that all namespaces that are in scope for the literal result element in the stylesheet are copied to the result document, and thexsinamespace must be in scope here, or the stylesheet fragment would not be valid.Other books