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RE: My report on experiments with unused namespaces

• From: "Costello, Roger L." <costello@mitre.org>
• To: "xml-dev@lists.xml.org" <xml-dev@lists.xml.org>
• Date: Wed, 15 Sep 2010 17:45:10 -0400

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

• Follow-Ups:
  • RE: My report on experiments with unused namespaces
    • From: Amelia A Lewis <amyzing@talsever.com>
  • Re: My report on experiments with unused namespaces
    • From: David Carlisle <davidc@nag.co.uk>

• References:
  • My report on experiments with unused namespaces
    • From: "Costello, Roger L." <costello@mitre.org>
  • Re: My report on experiments with unused namespaces
    • From: Amelia A Lewis <amyzing@talsever.com>
  • Re: My report on experiments with unused namespaces
    • From: Michael Kay <mike@saxonica.com>
  • RE: My report on experiments with unused namespaces
    • From: "Costello, Roger L." <costello@mitre.org>
  • Re: My report on experiments with unused namespaces
    • From: David Carlisle <davidc@nag.co.uk>