[lojban] Re: nai in UI (was: BPFK phpbb)

[Jim Carter <jimc@MATH.UCLA.EDU>]

On Thu, 1 May 2003, And Rosta wrote:
> But I opine that a syntax tree is valid only if it is the syntax tree of
> some sentence, and since a sentence is a pairing of a sound and a meaning,
> a syntax tree is valid only if it yields a meaning.

Well, that's where we differ, and I think the difference is important.
Take for example the distinction between:

    54 68 65 72 65 20 69 73 20 61 20 63 72 6f 63 6f
    64 69 6c 65 20 69 6e 20 74 68 65 20 62 61 74 68
    74 75 62

and "There is a crocodile in the bathtub".  There is a whole lot of
processing between the first one and the second.  To demolish a straw man,
the representation in octets is certainly valid (as a representation of a
byte string in hex).  You're not going to deny that, are you, despite the
fact that there's a subtle flaw that invalidates the utterance at the final
stage of processing.

A major lesson of 20th century system design is, you get a lot more value
for your effort if you make things modular, with well-defined interfaces
that are not penetrated.  In our context, lexing and parsing should be
independent, and both should be isolated from semantic analysis.  <phma>
made a related point in his reply.  In natlangs, meaning "informs" grammar,
but Chomsky's lesson is that natlangs have a grammar that can be expressed
with minimal reference to meaning.  Not to say that every natlang conforms
perfectly to this ideal, but even English comes pretty close.  The Lojban
grammar was created to refer to meaning only at the level of the syntactic
category of the various words, and I think that design principle should
remain unchanged.

> I contend (a) that if we are dealing with language then we have to
> engage with this notion of meaningfulness, since language is intrinsically
> meaningful -- if you don't have meaning then you don't have language --
> and (b) that a logical language like Lojban ought to spend a lot of
> energy on firming up the definition of meaningfulness (e.g. a well-formed
> logical formula, augmented by extralogical stuff like attitudinality
> etc.).

Oh, yes, certainly, I agree with you 100%, and I think that there hasn't
been enough attention paid to the last (and hardest) step, semantic
analysis.  But General February advises, don't split your force, or
conversely, each module should deal with only the task assigned to it, and
not fritter away its unity and effectiveness dealing with the tasks of
other modules.  Specifically, the semantic analyser depends on the parser
realizing the agreed-on grammar, and that's all the parser should do.  The
parser should not be called on to recognize a misplaced kau; that
positively ought to be left to a later stage, semantic analysis.

(p.s.: The subtle flaw is a missing period, making the utterance not a
statement and not useful as a warning.  A Real Human could do error
recovery, and each stage of processing should have error recovery features
as much as practical, but of course the core task comes first: correctly
processing valid utterances, and tagging garbage even if the program is
too dumb to clean it up.)

James F. Carter          Voice 310 825 2897    FAX 310 206 6673
UCLA-Mathnet;  6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA  90095-1555
Email: jimc@math.ucla.edu    http://www.math.ucla.edu/~jimc (q.v. for PGP key)