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

[Alan Post <alanpost@sunflowerriver.org>]

On Sat, Apr 10, 2010 at 10:47:56AM -0400, Kevin Reid wrote:
> 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,

Thank you for this.

I was writing C code for many years before I began to study the
grammar, and my experience of learning the formal grammar for C
was one of joy--I saw the language in an entirely new way and I
think it made me a better programmer.

I've struggled understanding the formal grammar for Lojban, and
I've assumed it was my inexperience as a whole with the language.
I certainly plan for some part of my future study of Lojban to
include a more rigorous understanding of the formal grammar, but
your hints hear really speak to why the technique I've used so
far to understand it has been difficult.

And +1 on your suggestion of transforming the grammar into something
that would be easier to write software for interpretation.  I can
peform my future study with an eye toward this as well.

Thank you!

-Alan
-- 
te djuno lo do sevzi

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