2. xml-namespaces
TRANSCRIPT
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 2/14
Module Introduction
Welcome to the module, Namespaces.
This module introduces XML Namespaces
and the reasons for using Namespaces in
XML documents.
This module aims at giving a clear
understanding of Namespaces syntax.
In this module, you will learn about:
XML Namespaces
Working with Namespaces Syntax
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 3/14
#1 - XML Namespaces Lesson Overview
Identify the need for a namespace.
Define and describe namespaces in XML.
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 4/14
Need for a Namespace
In XML, element names are
defined by the developer.
This often results in a conflict
when trying to mix XMLdocuments from different XML
applications.
XML Namespaces Provide a
method to avoid element nameconflicts.
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 5/14
Define Namespaces
In XML, elements are distinguished by using namespaces.
XML Namespaces provide a globally unique name for an elementor attribute so that they do not conflict one another.
A namespace is a collection of names that can be used aselement names or attribute names in XML document.
Namespaces allow the browser to:
Combine documents from different sources, and help identify thesource of elements or attributes.
Access DTD or other description of the elements and attributesagainst which, the document is validated.
A Namespace is identified by the URI.
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 6/14
#2 - Working with Namespaces Syntax
Explain the syntax for XML namespaces.
Discuss attributes and namespaces.
Discuss how to use default namespaces.
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 7/14
Solving the Name Conflict
by Pref ixing element names
There will be no conflict because the two <table> elements havedifferent names.
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 8/14
XML Namespaces Syntax- The “xmlns” Attribute
When using prefixes in XML, aso-called namespace for theprefix must be defined.
The namespace is defined bythe “xmlns” attribute in the
start tag of an element.
Syntax:xmlns:prefix ="URI "
Prefix must not begin with
“xml” or “xmlns”
The namespace URI is not usedby the parser to look upinformation
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 9/14
XML Namespaces - The “xmlns” Attribute
Namespaces can be declared:
1. In the elements where they are used
2. In the XML root element
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 10/14
Placing attributes in a namespaces
Attribute belong to particular elements and they are not a part
of namespaces, even if the element is within some
namespaces
If an attribute name has no prefix, it has no namespace.
An attribute without a prefix is in default namespaces.
If an attribute name has a prefix, its name is in the namespaces
indicated by the prefix.
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 11/14
Placing attributes in a namespaces
Syntax
Example
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 12/14
Default Namespaces
Defining a default namespace for an element saves us from usingprefixes in all the child elements.
Syntax: xmlns="URI "
7/30/2019 2. XML-Namespaces
http://slidepdf.com/reader/full/2-xml-namespaces 13/14
Override default namespaces
The default namespaces applies to the element on which it wasdefined and all descendant of that elements
If one of the descendants has another default namespaces defineson it, this new namespace definition overrides the previous oneand become the default for that element and all its descendents.