Web Technology - Old Questions
13. Write short notes on:
a) XML Namespace
b) HTML DOM
a. XML Namespace
XML Namespace is a mechanism to avoid name conflicts by differentiating elements or attributes within an XML document that may have identical names, but different definitions.
Consider two XML fragment:
//1.xml
<table>
<tr>
<td>Apples</td>
<td>Bananas</td>
</tr>
</table>
//2.xml
<table>
<name>African Coffee Table</name>
<width>80</width>
<length>120</length>
</table>
If these XML fragments were added together, there would be a name conflict. Both contain a <table> element, but the elements have different content and meaning.
Name conflicts in XML can easily be avoided using a name prefix.
E.g.
<h:table>
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>
<f:table>
<f:name>African Coffee Table</f:name>
<f:width>80</f:width>
<f:length>120</f:length>
</f:table>
In this example, there will be no conflict because the two <table> elements have different names.
b. HTML DOM
The HTML DOM is an Object Model for HTML. It defines:
- HTML elements as objects
- Properties for all HTML elements
- Methods for all HTML elements
- Events for all HTML elements
When a web page is loaded, the browser creates a Document Object Model of the page. The HTML DOM model is constructed as a tree of Objects:
