The SGML class library package

This is a set of generic classes for dealing with normalised document instances for any SGML DTD. They do not include a validating parser yet, though I am moving towards being able to validate XML. (Jan 1997)

An application (or possibly an applet) built with these classes will read a normalised SGML file , such as proposed by the XML project. It decides what the DTD is and downloads a corresponding class library. If one DTD 'includes' another it can cater for that.

The advantage of this approach is that it is simple to write postprocessing ('rendering') software for each DTD and to load this dynamically. This has already been done for CML - Chemical Markup Language - where most of the SGML ELEMENTs ('tags') have a Java class. (Alternatively it is possible to use a generic class for a group of ELEMENTS). These act rather like style-sheets - but much more powerful - for applications which are non-textual.

Some key components of the package are

DTD Represents a generic DTD - all DTDs are subclassed from this
GI Represents a generic Identifier. Corresponds roughly to the ELEMENT declaration in the DTD.
SGMLNode An SGML ELEMENT (represented as a node in an tree). SGMLNodes can contain content, which is a mixture of other nodes and PCDATA
SGMLNodeIndexSet A list of nodes; useful for representing searches
SGMLAttribute An SGML Attribute. Contains a name and an value.
SGMLAttlist A list of attributes (corresponds to ATTLIST)
SGMLTree The parse tree of an SGML document, consists of nodes.
SGMLTOC The graphics representation of an SGMLTree (as a dynamically configurable TableOfContents).
SGMLStream Input to the SGML parser. Must be well-formed SGML - does not validate yet.
ESISStream Alternative input to the SGML parser. Produced by tools such as sgmls.
DrawableSGMLNode The graphical representation of a node. Nodes have a display() method and can have icons, etc.
PCDATA Embryonic class for PCDATA
EntitySet Manages character Entity sets.
SGMLApplet Manages the SGMLTree as an applet.
SGMLUserClass An embryonic tool for supporting searches
BookmarkWindow A visual history of browsing the SGMLTOC.

In addition there are embryonic containers for the ELEMENTS in the HTML DTD.

Here are the classes in the package

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