🚀 go-pugleaf

In article <9208040136.AA09339@ucbvax.Berkeley.EDU> DRMACRO@RALVM13.VNET.IBM.COM ("Dr. "Eliot Kimber" Macro") writes:
>References:  <1992Aug4.005005.29589@news.eng.convex.com>
>
>I think I see what you're getting at.  I guess I don't
>make a distinction between declarative and structural.
>Or rather, if its declarative, it must also be structural,
>and then the only question is how useful is your declaration.
>Said another way, is there any useful difference between
>these two:
>
>.*-- Begin italic font
>.bf italic
>This is italic
>.*-- restore previous font
>.pf
>
>and
>
><italic>this is italic</italic>
>
>I would suggest that there is no useful difference, and that
>the use of SGML in the second case buys you little, if anything.
>
The biggest thing it buys is that one can validate the use of
<italic> tags (suppose they're not allowed in titles...) and
you can't do any validation on troff -- or any turing complete
procedural markup language.

Declarative systems usually evolve after considerable work on
a problem. The first solution to most problems is to establish
a few primitives and use loops, variables, and programming
constructs to complete the semantics. The resulting code
is somewhat difficult to maintain.

After some study, usually the boilerplate code is separated from the
real information, and eventually, a declarative system evolves.

Case in point: lex for lexical analysis and yacc for parsing,
UIL for interface description, etc.

Consider the difference between an X resource file and an emacs
lisp file. They're both used to set user options, but an X resource
file is declarative where an emacs lisp file is procedural. We
can do all sorts of validating and database oriented processing
on the X resource file, but the only thing we can do with the elisp
file is interpret it.

So while I agree that delcarative markup systems should also be
structural markup systems, I think they are still separate issues.
The format/structure distinction is somewhat unique to text
processing systems. The procedural/declarative distinction is
more of a general computing distinction.

Dan