Приложение E: Применимость и расширяемость CSS1
(Это приложение является
информативным, а не формальным)
The goal of the work on CSS1 has been to create a
simple style sheet mechanism for HTML documents. The current
specification is a balance between the simplicity needed to
realize style sheets on the web, and pressure from authors for
richer visual control. CSS1 offers:
CSS1 does not offer:
- per pixel control: CSS1 values simplicity over
level of control, and although the combination of
background images and styled HTML is powerful, control to
the pixel level is not possible.
- author control: the author cannot enforce the use
of a certain sheet, only suggest
- a layout language: CSS1 does not offer multiple
columns with text-flow, overlapping frames etc.
- a rich query language on the parse tree: CSS1 can
only look for ancestor elements in the parse tree, while
other style sheet languages (e.g. DSSSL [6]) offers a
full query language.
We expect to see extensions of CSS in several
directions:
- paper: better support for printing HTML documents
- support for non-visual media: work is in the
process to add a list of properties and corresponding
values to support speech and braille output
- color names: the currently supported list may be
extended
- fonts: more precise font specification systems
are expected to complement existing CSS1 font properties.
- values, properties: we expect vendors to propose
extensions to the CSS1 set of values and properties.
Extending in this direction is trivial for the
specification, but interoperability between different UAs
is a concern
- layout language: support for two-dimensional
layout in the tradition of desktop publishing packages.
- other DTDs: CSS1 has some HTML-specific parts
(e.g. the special status of the 'CLASS' and 'ID'
attributes) but should easily be extended to apply to
other DTDs as well.
We do not expect CSS to evolve into:
Copyright
_ї_ 1996 W3C
(MIT,
INRIA,
Keio
), All Rights Reserved. W3C liability,
trademark,
document
use and software
licensing rules apply.
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