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How does the specification file tell sgmlspl what to do?

sgmlspl uses an event model rather than a procedural model -- instead of saying "do A then B then C" you say "whenever X happens, do A; whenever Y happens, do B; whenever Z happens, do C". In other words, while you design the code, sgmlspl decides when and how often to run it.

The specification file, which contains your instructions, is regular perl5 code, and you can define packages and subroutines, display information, read files, create variables, etc. For processing the SGML document, however, sgmlspl exports a single subroutine, sgml(event, handler), into the 'main' package -- each time you call sgml, you declare a handler for a specific type of sgmls event, and sgmlspl will then execute that handler every time the event occurs. You may use sgml to declare a handler for a generic event, like 'start_element', or a specific event, like '<DOC>' -- a specific event will always take precedence over a generic event, so when the DOC element begins, sgmlspl will execute the '<DOC>' handler rather than the 'start_element' handler.

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