You may recall that the declaration of a namespace includes a namespace prefix and a namespace name. Consider the example

<root xmlns:pre='http://myserver.com'>

where 'pre' is the prefix and 'http://myserver.com' is the name. Keep in mind that there are some constraints to the naming of a prefix: It must begin with an underscore or a letter (a..z, A..Z). In addition, the prefix cannot begin with the sequence of letters x, m, l in any combination of upper or lower case. The prefix 'xml' is by definition associated with the name
http://www.w3.org/XML/1998/namespace Also, the prefix 'xmlns' is used for binding namespace and is also reserved.