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Re: Quiz: how many namespaces are in scope?

• From: Evan Lenz <evan@evanlenz.net>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Mon, 30 Aug 2010 11:39:46 -0700

Hi Roger,

The only thing I'd change is that it is not illegal to declare the xml 
namespace, provided you use the correct namespace URI. "It MAY, but need 
not, be declared, and MUST NOT be bound to any other namespace name." [1]

In my XPath/XSLT training classes, I like to ask this quiz question: How 
many namespace nodes are in this document? People are usually surprised 
when they hear the answer is (for this case) 21.

Evan

-- 
Evan Lenz
Lenz Consulting Group, Inc.
http://lenzconsulting.com
+1 (360) 297-0087


[1] http://www.w3.org/TR/xml-names/#xmlReserved

Costello, Roger L. wrote:
> Hi Folks,
>
> Consider this XML document:
>
> <?xml version="1.0"?>
> <N1:NumberList xmlns:N1="http://www.example1.org"
>                xmlns:N2=" http://www.example2.org ">
>         <Number>23</Number>
>         <Number>41</Number>
>         <Number>70</Number>
>         <Number>103</Number>
>         <Number>99</Number>
>         <Number>6</Number>
> </N1:NumberList>
>
> For the first child element: 
>
>         <Number>23</Number>
>
> what namespaces are in scope?
>
> I created an XSLT template to output the <Number> element's in-scope namespaces:
>
> -------------------------------------------
> <xsl:template match="*">
>        <xsl:for-each select="namespace::*">
>            <xsl:value-of select="."/></p>
>        </xsl:for-each>
> </xsl:template>
> -------------------------------------------
>
> Here is the output:
>
>       http://www.w3.org/XML/1998/namespace
>  
>       http://www.example1.org
>  
>       http://www.example2.org
>
> There are three (3) in-scope namespaces.
>
> Lesson Learned: Implicit on the root element of every XML document is this namespace declaration:
>
>       <root xmlns:xml="http://www.w3.org/XML/1998/namespace">
>
> NOTE: it is illegal to explicitly declare the xml namespace. The xml namespace is built into every XML application.
>
> Since the xml namespace is implicitly declared in every XML document, you can immediately use the xml:lang attribute and the xml:space attribute, e.g.,
>
> <movie>
> 	<title>The Laughing Cow</title>
> 	<title xml:lang="fr">La Vache Qui Rit</title>
> </movie>
>
> Here is an XSLT template to output the in-scope namespaces and their prefixes:
>
> -------------------------------------------
> <xsl:template match="*">
>         <xsl:for-each select="namespace::*">
>             Namespace in scope = <xsl:value-of select="."/>
>             Namespace prefix = <xsl:value-of select="name(.)"/>          
>         </xsl:for-each>
> </xsl:template>
> -------------------------------------------
>
> Here is the output:
>
>       Namespace in scope = http://www.w3.org/XML/1998/namespace
>       Namespace prefix = xml 
>
>       Namespace in scope = http://www.example1.org
>       Namespace prefix = N1
>
>       Namespace in scope = http://www.example2.org
>       Namespace prefix = N2
>
> QUESTIONS
>
> 1. Have I correctly analyzed the situation (regarding in-scope namespaces)?
>
> 2. What else would you add?
>
> /Roger
>
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• Follow-Ups:
  • Re: Quiz: how many namespaces are in scope?
    • From: Amelia A Lewis <amyzing@talsever.com>

• References:
  • Quiz: how many namespaces are in scope?
    • From: "Costello, Roger L." <costello@mitre.org>