Just as the W3C is finishing up XHTML 1.0, recasting
HTML 4.0 into an XML
grammar, ISO has released a Draft International Standard of its version
of HTML, building on the
W3C's HTML 4.0 recommendation with additional
SGML-specific material.
ISO/IEC 15445:1999 goes in some different directions than XHTML. Most obviously, ISO has kept
upper-case representations of all the element and attribute names. Case-sensitivity is discussed in particular
situations, but otherwise ISO/IEC 15445 makes very few demands regarding case. (Unlike XML, SGML
permits case folding.) This version of HTML
includes an SGML declaration for use with SGML processors handling HTML, and describes how
'validating HTML systems' should process HTML. Unlike XHTML, it subsets HTML 4.0 rather than
preserving all of its contents.
The ISO version of HTML stays out of the multiple DTDs/namespaces issue that confounded XHTML 1.0.
While two DOCTYPE declarations are permitted ("ISO/IEC 15445:1999//DTD HyperText Markup
Language//EN" and
"ISO/IEC 15445:1999//DTD HTML//EN"), they both reference the same DTD. The standard also
provides an architectural forms declaration for HTML 4.0, and specifies additional character encoding
handling.
Robin Cover's SGML/XML Web Page has additional information on this and
other
standards efforts related to SGML and XML.