Re: [gobo-eiffel-develop] RelaxNG code generator

[Cheng-Chang Wu <che...@ya...>]

--- Colin Adams <col...@ho...> 說：

> 
> What's it supposed to do?
> 
> I looked at the files you suggested, and they don't
> tell me.
> 

Thank you for your asking.

It a tool for generating eiffel source code from a
given RELAX NG grammar. By embedding code fragments in
the grammar, you can take appropriate actions while
parsing valid XML documents against the grammar.

In gerng.e the feature 'build_start_state' is
generated from gerng.rng. Feature build_start_state
builds a finite state machine. In the case of gerng
the state machine is a executable RelaxNG
specification, i.e gerng.rng is a simplified version
of RelaxNG specification with some eiffel code
embedded in it with tag <eiffel:start> or
<eiffel:exit>. Tag <eiffel:start> specified what
action should be done before entering a state. Tag
<eiffel:exit> specified what should be done upon
leaving a state. The text part of <eiffel:start> and
<eiffel:exit> should be an eiffel agent. 

If you can compile gerng.e, you can try 'gerng
gerng.rng' . It will output the feature
build_start_state to standard output. You can then run
gerng on other RelaxNG files. If your RelaxNG files
don't have <eiffel:enter> or <eiffel:exit>, the
generated FSM can be used as validator to check input
against the RelaxNG specification.

I have no time to implement the optimizations proposed
in james clark's paper under the titles 'Avoiding
exponential blowup' and 'Memoization'.

It was fun to develop gerng. At beginning I must write
a buggy build_start_state myself, applied it on a
simplified gerng.rng, generated a improved version of
build_start_state.   Then I improved the gerng.rng
further to include more RelaxNG elements. I hope it
has covered all elements of RelaxNG, but I'm not sure.

I used it in my project to validate xml messages
defined with RelaxNG and generate commands from the
validated xml messages.

Cheng-Chang Wu

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