XSLT and XPATH: A Guide to XML Transformations

12.3. Namespaces

Namespaces identify the particular markup vocabulary from which element-type names and attribute names are derived. They are important because, for example, when using links, the idea of embedding linked content from other documents raises the problem of possible duplicate element-type names and attribute names with different meanings. For instance, if the element-type name “body” was used in two different ways, such as by an auto parts manual and by a physician's desktop reference, how should this be handled?

It is essential that element-type names and attribute names be distinguishable in the way that, for example, the particular meaning of element in chemical element is distinguishable from its meaning in markup element.