Differences between version 2 and predecessor to the previous major change of SGML.
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| Newer page: | version 2 | Last edited on Monday, October 6, 2003 1:51:00 pm | by AristotlePagaltzis | Revert |
| Older page: | version 1 | Last edited on Thursday, July 25, 2002 10:00:52 pm | by WikiAdmin | Revert |
@@ -1,20 +1,11 @@
[Acronym] for __S__tandard __G__eneralized __M__arkup __L__anguage.
-----
-From http://whatis.techtarget.com/definition/0,,sid9_gci214201,00.html:
-SGML (Standard Generalized
Markup Language) is
a standard for
how to specify a document markup language or tag set
. Such a specification is itself
a document type definition (
[DTD])
. SGML is not
in itself
a document language
, but a description
of how to specify one. It
is metadata
+It evolved from earlier generalized markup languages developed at [IBM], including General
Markup Language (GML
) and ISIL. Despite the name, it's not itself
a markup language, but a description of
how to specify one
. Such a specification is called
a [DTD]; a good example for MetaData
. The premier markup language defined in terms of [
SGML]
is [HTML]. While disregarded
in [HTML] for
a long time
, the philosophy
of [SGML]
is that documents should be described in terms of their structure, rather than the "document image". They can then be displayed or output in any form appropriate for any media.
-SGML is based on
the idea that documents have structural and other semantic elements that can be described without reference
to how such elements should be displayed
. The actual display
of such a document may vary
,
-depending on the output medium
and style preferences
. Some advantages
of documents based on SGML are:
+However,
the standard is excessively complex, so no [SGML] parser
to date supports all of the standard's features
. Many
of these were added to cater to humans writing [SGML] documents manually
, but more
and more markup is machine generated
. This situation eventually led to the creation
of [XML].
-* They can be created by thinking in terms of document structure rather than appearance characteristics
(which may change over time
).
-* They will
be more portable because an SGML compiler can interpret any document by reference
to its document type definition (
[DTD])
.
-* Documents originally intended for the print medium can easily be re-adapted for other media
, such as the computer display screen.
+sgmlnorm
(1
) can
be used
to check whether [SGML] documents validate against their
[DTD]. F.ex
, if a [HTML] file contains a proper document type declaration like
-The language that this Web browser uses, Hypertext Markup Language ([HTML]), is an example of an SGML
-based language. There is a document type definition for HTML (and reading the
HTML specification is effectively reading an expanded version of the document type definition)
.
+ <!DOCTYPE html PUBLIC "
-//W3C//DTD
HTML 4
.01//EN">
-SGML is based somewhat on earlier generalized markup languages developed at
[IBM
], including General Markup Language
(GML
) and ISIL
.
-
------
-
-XML
] is a simplified version of [SGML] when
the discovered that noone understood
[SGML], and only used a handful of features
.
+then sgmlnorm(1) can validate it against
[W3C
]'s __strict.dtd__ and report any violations
(such as having text not contained in __<P>__ or __<DIV>__ tags
). [Debian
] users can install
the __sp__ package to get this and other
[SGML] parsing tools
.
