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SGML stands for Standard Generalized MarkUp
Language. SGML is a formal system designed for building text
markup languages. It is an internationally recognized standard
for text information processing that provides an organized
way to structure content for broad use. Documents marked according
to rules outlined in SGML have two basic elements: the content
and information about the content.
SGML is platform independent, requiring
only a computer and the appropriate software to analyze the
documents to make sense of the data. A piece of software that
reads and analyzes a SGML document is called an SGML parser.
| Defining an SGML Application |
From SGML's point of view, a document is
a hierarchical structure of nested elements. SGML defines
the structure of a particular type of document via what is
called a document type definition (DTD). An SGML declaration
is a formal construct used to specify general information
about an SGML application for HTML 4 provided by W3C.
As for the syntax of the SGML declaration
and DTD, they largely consist of statements enclosed in angle
brackets(<>). Each one starts with a ! character and
a keyword or name followed by one or more parameters seprated by spaces.
The SGML declaration is contained in the
SGML statement, which has the folowing syntax:
<!SGML "ISO 8879:1986"...>
The ellipsis here represents the body of the SGML declaration,
and the string ISO 8879:1986 denotes the level of SGML standard
that this declaration confirms to.
Everything within a <! statement enclosed
in double hyphens (--) is ignored by the SGML parser.
Example:
<!ELEMENT IMG --O
EMPTY -- Embedded Image-->
In the above code line, the words Embedded Image are intended as a comment.
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