Runtime "learning"

Hi!


I am working on my master's thesis at the Department of Computer
Science at the University of Oslo. In this setting, I would appreciate
if you could provide me with some clarification on the following
issue:


In my work, within Open Distributed Processing, I will end up
proposing an IDL-like language designed for specifying stream and flow
interfaces, which, like any other IDL, must be translated to stubs in
some programming language (C++).


However, I would like to build a parser which learns the grammar of
the IDL-like language at runtime. In other words, I want it to read
some templates of some kind, and then recognize sentences conforming
to the language described in those templates. In this way, when
updating the language, the parser doesn't need to be compiled again.


I am considering a tool called PCCTS which has taken away the pain of
writing parsers, Abstract Syntax Trees builders and Abstract Syntax
Trees Walkers by hand. If I understand the documentation correctly,
one only needs to define the language by means of its (potentially
augmented) grammar, and then, after fixing an automatically generated
makefile, "make" it.


What I am asking for is: Is there any tool which can take me a step
further? Can it build an EXECUTABLE file, which, AT RUNTIME, learns a
language by reading its grammar, and thus becames able to recognize
(and take actions based on) sentances in that language?


Any tool which can learn at least certain constructs of the language
at runtime?


Example:


I want my parser to recognize, among other things, the following:


                video_encoding = "MPEG";


"video_encoding" would be a keyword (token?) in my language, and "MPEG" a
legal value for that keyword. What I need is a way to extend the set of
keywords, and a way to extend the set of legal values belonging to each
keyword, without having to remake my parser.


PCCTS is great, but we are never satisfied, are we? :-)


Any help is appreciated,
Catalin
[You can certainly use PCCTS to generate C code, compile it into a
shared library module and load it, but if you really want runtime
syntax definitions you might look at the extensible language work
from the 1970s. -John]

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