Date: Sun, 27 Mar 1994 17:41:57 +0200
Message-Id: <9403271541.AA25748@dxmint.cern.ch>
From: hallam@alws.cern.ch
Subject: Re Formalisms for IIA [Was: LISP for Complex URC Sytax]
PhB here...
Dan Writeth:-
*
*>I think we should aim rather on minimizing the complexity of the parser.
*
*I agree. My experience says that if it can't be expressed in some
*formalism (like lex and yacc) in a page or two, then it's too complex
*and it won't be implemented consistently.
*
*> Having
*>a different syntax is not necessarily that much of a problem. Anyone writing a
*>
*>HTTP system in any case begins by writing an FSR compiler at the least.
*
*FSR compiler... is this something like lex? I hope HTTP implementors
*don't need one of these, though I agree it's usefull in this context.
*
Too late I've written one :-)
Actually I've written about 10 FSR type systems over the past few
years. One more won't hurt. LEX is a complete pain too use and
I don't recommend it. Its actually easier to think in terms
of FSMs than the convoluted REs of LEX.
*
*>If we want a simple system we use LISP. If we want a standard we should use
*>ASN.1
*
*How about using ASN to define the essential nature of the beast, and
*specifying a LISP encoding so that it can be parsed easily?
*
All we need is a data structure. From that I can synthesize a binding
in ASN.1, LISP, Goedel or whatever. No hassle. Could even do SGML
if must.
*
*SGML is designed for situations where most of what you're dealing with
*is text -- there's just a little markup here and there. So it's ok to
*make the markup verbose in order to encoding text convenient. But with
*highly structured collections of small objects, it's a pain.
*
Quite right. The surest way to make any tool look stupid is to
use it in a completely inappropriate context.
*>I think we should do this anyway. I have been ripped of to the tune of 50quid
*>for the SGML manual. I find it marginaly less readble than the MVS debugger
*>manual.
*
*Apparently, nobody is expected to actually read the SGML standard.
*Folks are supposed to read the handbook by Charles Goldfarb. I'm not
*sure what the purpose of the standard is, exactly: it's not
*sufficiently formal to specify the language without further
*explanation, and yet it doesn't provide that very explanation.
The handbook is the standards docs loosly connected with hype.
*Agreed. Seconded. Amen. Though there is apparently a body of reasearch
*regarding formal properties of SGML. It seems pretty bass-ackwards to
*me. Had they discovered the formal properties of the language before
*writing the standarnd, I expect an SGML parser would be a one
*person-month project, rather than a hundred person-month project as it
*is.
>From the lectures Tony Hoare gave us the one thing he did hammer on
about was `formal systems are not a bolt on afterthought'. I
beleive him.
Phill H-B