Datasheet

Part I ✦ Introducing XML

CSS

Because XML allows arbitrary tags in a document, the browser has no way to know

in advance how each element should be displayed. When you send a document to a

user, you also need to send along a style sheet that tells the browser how to format

the tags you’ve used. One kind of style sheet you can use is a CSS style sheet.

Cascading style sheets, initially invented for HTML, define formatting properties such

as font size, font family, font weight, paragraph indentation, paragraph alignment,

and other styles that can be applied to particular elements. For example, CSS allows

HTML documents to specify that all

H1 elements should be formatted in 32-point,

centered, Helvetica bold. Individual styles can be applied to most HTML tags that

override the browser’s defaults. Multiple style sheets can be applied to a single

document, and multiple styles can be applied to a single element. The styles then

cascade according to a particular set of rules.

CSS rules and properties are explored in more detail in Chapters 12, 13, and 14.

Mozilla, Opera 4.0, Netscape 6.0, and Internet Explorer 5.0 and later can display

XML documents with associated CSS style sheets. They differ a little in how many

CSS properties they support and how well they support them.

XSL

The Extensible Stylesheet Language (XSL) is a more powerful style language designed

specifically for XML documents. XSL style sheets are themselves well-formed XML

documents. XSL is actually two different XML applications:

✦ XSL Transformations (XSLT)

✦ XSL Formatting Objects (XSL-FO)

Generally, an XSLT style sheet describes a transformation from an input XML docu-

ment in one format to an output XML document in another format. That output

format can be XSL-FO, but it can also be any other text format (XML or otherwise),

such as HTML, plain text, or TeX.

An XSLT style sheet contains templates that match particular patterns of XML ele-

ments. An XSLT processor reads an XML document and an XSLT style sheet and

compares the elements it finds in the document to the patterns in the style sheet.

When the processor recognizes a pattern from the XSLT style sheet in the input

XML document, it instantiates the template and outputs the resulting text. Unlike

cascading style sheets, this output text is somewhat arbitrary and is not limited to

the input text plus formatting information. It depends on the instructions in the

template.

Cross-

Reference

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