IBM Version 5 manual XML namespaces, Example 2-1 a namespace example

used with XML if the display engine supports it. So far, the only shipping browser that supports this feature is Microsoft Internet Explorer 5.0.

CSS can be used within a document, or referenced in a separate stylesheet, which is the more common approach. For more information on CSS, see:

http://www.w3.org/TR/CSS1

The Cascading Style Sheet, Level 1 (CSS1) was made a full recommendation in 1996, while Cascading Style Sheet, Level 2 (CSS2) was made a full recommendatory in 1998. CSS2 built upon CSS1, but had made no major changes.

It can be said that CSS1 was a simple specification. It has a few limitations: It did not say anything about tables on a HTML page. CSS2 did try to rectify this, by introducing a new set of properties and behaviors, but these have not been supported.

CSS1 does not incorporate absolute positioning within a table. It is possible to define position relatively. The specification for CSS2 has devoted a number of chapters for visual rendering, which includes the positioning of elements.

W3C has also published a working draft on CSS3 on its Web site in May 2001. The main aim was to modularized the CSS specification. It is intended to clarify the relationships between the different parts of the specification, and to reduce its size.

2.4 XML namespaces

Namespaces are used when there is a need for elements and attributes of the same name to take on a different meaning depending on the context in which they are used.

For instance, a tag called <TITLE> takes on a different meaning, depending on whether it is applied to a person or a book. If both entities (a person and a book) need to be defined in the same document, for example, in a library entry which associates a book with its author, we need some mechanism to distinguish between the two and apply the correct semantic description to the <TITLE> tag whenever it is used in the document. Namespaces provide the mechanism that allows us to write XML documents which contain information relevant to many software modules. Consider this example:

Example 2-1 A namespace example

<?xml version”1.0”?>

<library-entry xmlns:authr=”authors.dtd” xmlns:bk=”books.dtd”>

Chapter 2. Technologies in XML 23