Introduction to
                                           XML Namespaces

Web Engineering, SS 2007



Tomáš Pitner

                                       XML Namespaces – Why?

n     Part of the core XML standards family

  q    Namespaces in XML 1.0 (Second Edition)

  q    W3C Recommendation 16 August 2006



n     Mean enabling mixing more markups within one document

  q     XHTML with SVG (graphics) fragments

  q     XHTML with MathML (math notation) fragments

  

n     Each NS is uniquely identified by its URI

                                       XML Namespaces – What?

n     XML NS logically distinguishes so-called namespaces that apply to nodes in the doc

  

  q     For each NS, a separate schema (markup) may be defined / usually XML Schema, Relax NG…

  q     Not compatible with DTD – if namespaces are used, only limited use of DTD is possible

  q     NS applies only to elements and attributes

                                      XML Namespaces – Default

n     Default namespace

  q     Applies just to elements without prefix

  q     declared by xmlns=“URI” in the element or its ancestor

  q     always the nearest declaration applies!

  q     example:

    n      <party 
     xmlns="http://www.austria.gv.at/ns/1.0“
      url="http://www.spoe.at“>SPÖ</party>

                                     XML Namespaces – Prefixed

n     Prefixed namespace

  q     applies to elements and attributes with the prefix

  q     declared by xmlns:prefix=“URI” in the element or its ancestor

  q     always the nearest declaration applies!

  q     example:

    n      <breg:party 
     xmlns:breg="http://www.austria.gv.at/ns/1.0“
      url="http://www.spoe.at“>SPÖ</party>

  

                                       XML  Namespace Example

<?xml version='1.0' encoding='UTF-8'?>

<staff organization="Bundesregierung

       xmlns:breg=“http://www.austria.gv.at/ns/1.0"

       xmlns="http://generic-ns.org/ns/1.0">

  <person id="agu">

    <name>Alfred Gusenbauer</name>

    <breg:party url="http://www.spoe.at">SPÖ</breg:party>

  </person>

  <person id="wmo">

    <name>Wilhelm Molterer</name>

    <breg:party url="http://www.oevp.at">ÖVP</breg:party>

  </person>

</staff>



                                     XML Namespaces – Resources

n    The Specification on W3C

  q    http://www.w3.org/TR/REC-xml-names/

n    ZVON XMLNS Tutorial

  q    http://www.zvon.org/xxl/NamespaceTutorial/Output/index.html

n    W3Schools

  q    http://www.w3schools.com/xml/xml_namespaces.asp