Next Generation HTML: Style Sheets
June 7th 1998
Style appears above markup languages in our Big Picture.
Cascading Style Sheets (both CSS1 and the recently recommended
CSS2) provide content developers a way to centralize font, color,
layout, and other presentation aspects into one or more style
sheets, which are then referenced from HTML files. Changes to the
style sheets effect all pages which reference them. The WDVL
web site makes extensive use of
CSS1 style sheets;
see the
WDVL House Style.
With the acceptance of
Cascading Style Sheets,
Level 2 (CSS2) on May 12, 1998, the W3C appears to have made
CSS1 and CSS-P (Positioning HTML Elements with Cascading Style
Sheets) obsolete. CSS2 builds upon CSS1, provides targeting style
for different output devices (printers, aural devices, hand held
devices, etc.), supports content positioning, downloadable fonts,
table layout, and automatic counters and numbering. Unlike
CSS1, CSS2 has simple, direct support for XML.
However,
Extensible Style
Language XSL) is really what is needed to best apply style
to XML documents. The
Proposal for XSL
from Microsoft, ArborText, and Inso Corp. lists these strengths
that XSL provides (compared to CSS):
"The powerful capabilities provided by XSL allow:
- formatting of source elements based on ancestry/descendency,
position, and uniqueness
- the creation of formatting constructs including generated text
and graphics
- the definition of reusable formatting macros
- writing-direction independent style sheets
- extensible set of formatting objects"
Unfortunately, as the diagram shows, XSL is currently just a lowly
W3C Note. On the other hand, it is encouraging that according
to the
XSL page under the W3C Style
section, an XSL Working Draft is targeted for July
1998, with a Proposed Recommendation scheduled for May 1999. XSL
is generally a compatible subset of the non-W3C effort called
Dynamic Style Semantics
and Specification Language (DSSSL),
much as XML is a subset of the non-W3C SGML. We note that of all
the style specifications, DSSSL is the most complex.
Next Generation HTML: Scripting Efforts
Next Generation HTML: The Big Picture
Next Generation HTML: Linking Efforts
|
