If each vocabulary is given a namespace, the ambiguity between identically named elements or attributes can be resolved.
A simple example would be to consider an XML instance that contained references to a customer and an ordered product.
The specification is not entirely prescriptive about the precise rules for namespace names (it does not explicitly say that parsers must reject documents where the namespace name is not a valid Uniform Resource Identifier), and many XML parsers allow any character string to be used.
In version 1.1 of the recommendation, the namespace name becomes an Internationalized Resource Identifier, which licenses the use of non-ASCII characters that in practice were already accepted by nearly all XML software.
The Namespaces specification does not say what should happen if such a URL is dereferenced (that is, if software attempts to retrieve a document from this location).
[5] In general, however, users should assume that the namespace URI is simply a name, not the address of a document on the Web.
Applications should avoid attaching any significance to the choice of prefix, but the information is provided because it can be helpful to human readers.