Re: Stack-based human languages? (was Re: My Three Assertions)

Hallo!

On Mon, 28 Feb 2005 00:12:01 +0100,
Henrik Theiling <theiling@...> wrote:

> Hi!
>
> Jörg Rhiemeier <joerg_rhiemeier@...> writes:
> > > > Isn't that just a matter of staying within 7+-2 bounds? I don't see
> > > > anything inherently more difficult about the *syntax* that makes it
> > > > human-incompatible.
> > >
> > > I think so, too.  SOV and OSV syntax are just like Fithian.
>
> Ok, this statement was too absolute. :-)
>
> > I don't think so.
>
> Ok.
>
> > Fith allows a kind of stack acrobatic that goes well beyond anything
> > possible in human languages, in fact going beyond what human minds
> > can process in real time.  The resemblance of Fith to verb-final
> > human languages is only superficial.
>
> :-)
>
> Yes, the stack operations are special and crucial for distinguishing
> Fith from natlangs, that's true.  E.g. references to the nth stack
> cell, duplication, swapping etc. are very different from how natlangs
> work.
Yes.

> I just wanted to state that a stack is an appropriate data structure
> for many structures in natural languages.  The resemblance is not
> superficial, I think.  Only natural languages, in contrast to Fith, do
> not allow direct operations on the stack and they use it to a limited
> depth.
I know about the usefulness of stacks in language parsing, yes.  From
a half-forgotten lecture on compiler design, I remember that they are
frequently used for such purposes, even if the language parsed is not
overtly stack-based like Forth or Fith.  Whether the human brain uses
a stack, that's another question.  Certainly not in the same way as
the Fithian brain.  But I see what you mean.

> > >        A typical
> > > *long* Japanese sentence (or a long German sentence, too) uses a stack
> > > quite heavily.  It first pushes the nouns, then pops them with a verb,
> > > pushes back the combined concepts, pushes more nouns, and finally pops
> > > the rest.
> >
> > This is the first time I see any human language being described as
> > stack-based.
>
> Hehe. :-)
>
> But you saw them described as rules like
>
>    S -> NP VP
>
> right?
Yes.  S -> NP VP is a nice context-free rule, it is even in Chomsky's
Normalized Form.  (I'll disregard the question of the validity of the
VP node, here.)

>       And context-free grammars (which are not enough to describe
> human language, of course -- just a small excerpt from some grammars)
> are equivalent to stack automata.  Usually you start with a simple
> approach like this to seethe real problems of natural language
> processing.
Yes.

> > > Only a human language has a principle limitation in both the amount of
> > > words a concept can be remembered when it is not used (=life time of a
> > > stack cell) and the amount of data that can be remembered at the same
> > > time (=stack depth).
> >
> > These "limitations" are of such an importance that they render the
> > stack model of little use for describing human languages of any kind,
> > even verb-final ones.
>
> Reading my mail again I think I posed my point too radically.
> I actually fully agree with you. :-)
Good.

> > > ... daß Peter Maria Rolf  Essen  kochen     helfen     sehen      kann.
> > >        push  push  push  push   poppoppush poppoppush poppoppush poppush
> >
> > This is a rather contrived example.
>
> Yes. :)
>
> > Few if any German L1 speakers talk that way.
>
> Indeed.
>
> > And while a Fithian would parse it that way, I doubt that any human
> > would.  Human languages have tree-based structures with depth
> > limitations, not stack-based ones.
>
> Trees are the result of parsing a language using a stack-based
> machine.  Fith can be parsed into such trees as well.  The additional
> operations for stack manipulations to co-indexing etc. are different
> from what is usually needed for natural language processing, but there
> is a common basis.
>
> Still no? :-)
Now that you have stated your case, I understand how you arrived at
describing German subclauses as "stack-based".  I'd not say that any
human natlang is "stack-based", certainly not in the Fithian sense,
though stacks are certainly useful in parsing natlangs, and perhaps
each of us has some kind of stack somewhere deep in our brain ;-)

Greetings,

Jörg.