RE: [xml-dev] My report on experiments with unused namespaces

["Costello, Roger L." <costello@mitre.org>]

David Carlisle wrote:

> According to your definition of "unused" almost every XSLT stylesheet, 
> and a large proportion of XSD schema and RelaxNG schema use unused 
> namespaces. Are they all evil?

You are correct David. My definition of both "used" and "unused" namespace needs updating. 

Here goes.

[Definition] Used Namespace: a namespace in an XML instance document which is 

(1) used in an element name, or 

(2) used in an attribute name, or 

(3) used in a QName of an attribute value, or 

(4) used in a QName of an element value.

Example: This XML document illustrates the 4 locations where namespaces may be used:

<Root xmlns:NS1="http://www.namespaces.org/1";
      xmlns:NS2="http://www.namespaces.org/2";
      xmlns:NS3="http://www.namespaces.org/3";
      xmlns:NS4="http://www.namespaces.org/4";>
  
     <NS1:child NS2:attr="NS3:att-value">
         NS4:elem-value
     </NS1:child>

</Root>

[Definition] Unused Namespace: a namespace in an XML instance document which is 

(1) not used in an element name, and 

(2) not used in an attribute name, and

(3) not used in a QName of an attribute value, and

(4) not used in a QName of an element value. 

Example: In the following XML document this namespace is not used: http://www.namespaces.org/5

<Root xmlns:NS1="http://www.namespaces.org/1";
      xmlns:NS2="http://www.namespaces.org/2";
      xmlns:NS3="http://www.namespaces.org/3";
      xmlns:NS4="http://www.namespaces.org/4";
      xmlns:NS5="http://www.namespaces.org/5";>
  
     <NS1:child NS2:attr="NS3:att-value>
         NS4:elem-value
     </NS1:child>

</Root>

Do you agree? 

Have I identified all the locations where namespaces may be used?

/Roger