schemas.xhtml10.index.html Maven / Gradle / Ivy
Modularization of XHTML in RELAX NG
Modularization of XHTML in RELAX NG
This directory contains an implementataion in RELAX NG of the
modularization of XHTML specified by the Modularization of XHTML Recommendation.
The RELAX NG schema has not been mechanically derived from the DTDs.
Rather, it has been hand-crafted so as to produce a good quality RELAX NG
schema. However, it may well contain bugs.
The modules directory contains
all the modules; xhtml-basic.rng uses the
modules to implement XHTML
Basic; xhtml-strict.rng uses the
modules to implement XHTML
1.0 strict; xhtml.rng uses
the modules to implement the union of XHTML 1.0 transitional and XHTML 1.0 frameset. You can
download
everything as part of the main Jing distribution. To create a custom
version of XHTML, simply copy xhtml.rng and delete the
inclusions of the modules that you do not want.
The biggest difference between the RELAX NG implementation and the
DTD implementation is that the RELAX NG implementation does not
require you to create a model module specific to the combination of
XHTML modules you are using. Instead, simply include the modules you
want. The modules take care of redefining the content models
appropriately.
Note also the following differences:
- The frames module is used instead of the struct module, rather
than in addition to it.
- In the frames module, the
frameset element does not
restrict the optional noframes element to follow all the
other child elements. XHTML Modularization is inconsistent with both
HTML 4.0 and XHTML 1.0 here.
- In the basic tables abstract module, the
table
element does not have a width attribute. The XHTML Rec is
ambiguous here: the abstract module has the attribute, but the DTD
does not.
- The object and applet modules takes advantage of RELAX NG's
absence of restrictions on mixed content to enforce the requirement
that
params precede other content.
- The forms module takes advantage of RELAX NG's absence of
restrictions on mixed content to enforce the requirement that any
legend precedes other content.
- The RELAX NG schema does not enforce exclusions. The HTML 4 DTD
uses exclusions in several places, for example, to disallow an
a element from having an a element as a
descendant. It is not possible to represent this constraint in XML
DTDs. XHTML Modularization takes the approach of partially
representing this restriction by, for example, disallowing an
a element from having an a element as a
child, without disallowing it from having an a
element as a non-immediate descendant. This partial restriction has a
substantial cost in increasing the complexity and reducing the
modularity of the schemas. This implementation adopts a different
approach. The exclude directory
contains separate, independent RELAX NG schemas that enforce
exclusions. To check use of exclusions, a document should be
validated against each of these schemas that is applicable in
addition to being validated against the RELAX NG XHTML schema
proper. The available schemas are as follows:
exclude/basic.rng- checks the exclusions relating to
a and
pre elements
exclude/basic-table.rng- checks the exclusions relating to basic tables module (i.e.
checks that
table elements are not nested)
exclude/form.rng- checks the exclusions relating to forms and basic forms modules
James Clark