Re: [lojban] The efficacy of Lojban's grammar.

[Kevin Reid <kpreid@switchb.org>]

On Apr 10, 2010, at 9:51, And Rosta wrote:

> I wager that syntactic structures that would be assigned to Lojban  
> sentences by (1) syntacticians and (2) Lojban speakers would differ  
> very substantially from the syntactic structures assigned by the  
> formal grammar.

[Disclaimer: I Am Not A Linguist.]

In my experience developing software which works with the results of  
parsing using formal grammar (well, the PEG version), the trees  
produced by the formal grammar are not like how I internally think of  
Lojban grammar, but insofar as they are, *they aren't what I would  
design as a formal AST for Lojban either*.

In particular, the trees have a huge number of nodes which pertain  
only to the implementation structure of the grammar and are both  
redundant and unrelated to the semantics of Lojban. This falls out  
from the fact that the parser produces one tree node per nonterminal,  
named according to that nonterminal, unconditionally: no appropriate  
specialized actions/transformations have been defined.

There are two major problems with the usefulness of the produced parse  
trees:

  1. There are many nodes with exactly one child which reflect rules  
that
     exist only due to the factoring of the grammar, or nested cases  
in order
     to produce the proper parse tree for various optional clauses  
which
     usually don't exist.

  2. The nodes are named according to the nonterminal, not according  
to the
     matched rule. This means that the names reflect the syntactic  
role, the
     slot it fills, rather than what the slot was filled with. The  
result of
     this is that an interpretation of a given subtree has be  
inferred from
     the number and kind of child nodes rather than an actual symbol  
in the
     tree.

Particularly, note that the second problem is because the information  
*simply does not exist* in a formal system. The formal grammar(s) we  
have are simply defined to accept/reject sentences; the information  
about "what are these particular alternatives called" exists only  
informally in the CLL and other semantic-description documents.

So:

I agree that the formal grammar produces weird structures.

However, I believe it would be possible to create a parser, or  
transform the output of the current parser(s), such that the structure  
*is* similar to what a syntactician, or a Lojban speaker who is  
familiar with parsers and formal grammars (such as for programming  
languages), would assign.

Furthermore, I believe this particular project *should* be done, as it  
would (a) aid the development of computer software which interprets  
Lojban, and (b) be a useful tool in discussing “what does this Lojban  
sentence mean” and making sure that the semantics of Lojban are fully  
defined.

--
Kevin Reid                                  <http://switchb.org/kpreid/>




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