SGML on the Desktop / 1. An SGML system |
Figure 1: An SGML system. Bold italics indicates free tools. Bracketed terms are (free) standards, for which there is often further specialised support. |
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I have a picture of an SGML system in Figure 1. This shows the sequence of tools which are used to create and transform a document from its SGML original into whichever collection of output formats are required. The components here are:
The point of this is that the down-stream tools can now rely on getting a valid document, in just the format they want, with no surprises. This makes them a lot simpler, and makes some operations feasible.
The formatter doesn't refer to the DTD, because it is specific to a
single DTD (or perhaps to a family of related ones), and if you change
the DTD you'll have to change the formatter. The formatter will
typically depend on a stylesheet of some type, perhaps written in
DSSSL (Document Style and Semantics Specification
Language, an ISO standard) or XSL (XML Stylesheet Language, a
forthcoming W3C standard).
The usual SGML term for this is `down-conversion' (presumably because you're transforming the SGML document into a form with less information content), but `formatting' is possibly more intelligible.
I have described these components separately, to emphasise that they are conceptually distinct components of an SGML system. It might be most convenient for you to support these different phases with different tools, but there do exist tools which blur the components together.
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Norman Gray 21 July 1998 |