Subject: Re: [lojban] morphology

From: "Bob LeChevalier (lojbab)" <[email-masked]>
Date: Fri, 30 Nov 2001 23:37:22 -0500

At 09:58 PM 11/30/01 +0000, [email-masked] wrote:
>is it true that the lojban morphology is exaustively proven? that
>is, can it be shown that when following the morphology rules, audio
>visual isomorphism is assured?

It depends on what you mean by proven. We have a morphology algorithm that 
so far as we know follows the rules of the language that we have stated, 
and it will make a decision about whether words are or are not of various 
classes. But that algorithm does not distinguish between the various types 
of brivla - gismu, lujvo and fu'ivla are all members of "selma'o" BRIVLA 
(ignoring the fact that BRIVLA is not a category of cmavo). Thus 
"slinku'i" is a valid brivla form, but is not any of the valid types of brivla.

The algorithm has not been mathematically verified - we need someone with 
the right sort of mathematical proof-of-correctness skills to do that sort 
of thing, as the combinatorics form a VERY bushy tree (I think I estimated 
several million possible combinations to test in a string of only a dozen 
phonemes). However, we have dummy-checked all the common cases and any 
errors, if they exist, will involve weirdnesses in combinations of 
experimental cmavo and type IV fu'ivla and the like.

Nora has built a program that implements the algorithm, but since it does 
not distinguish between fu'ivla and lujvo and gismu, and you have to type 
stress explicitly, it is not a particularly useful thing. We've never 
found a bug when we've tried though.

>i was under the impression that it
>wasn't, and this was what was holding up cultural fu'ivla.

No. What holds up cultural fu'ivla is the very looseness of the algorithm 
for distinguishing classes of brivla. The three forms of brivla have a 
hierarchy. There are gismu first and foremost, then there are lujvo, which 
fit certain forms that do not break down in combinations with other words 
into a cmavo and a different lujvo and/or gismu, and the space of anything 
that is left, which will not break down alone or in combination into a 
gismu and/or lujvo and something else is a fu'ivla.

Given the hierarchy, there is little doubt that the algorithm will succeed 
in resolving all conflicts. However, since fu'ivla wordforms are defined 
in the algorithm only by what they are NOT, we do nopt have a definitive 
algorithm for testing a wordform to see if it is a valid fu'ivla. We know 
that "slinku'i" words fail the "slinku'i" test. We don't know what other 
wordforms within brivla space are not lujvo or gismu and which do not fail 
the test except by trial and error. The human process of testing words for 
possible breakup is sufficiently unintuitive and subject to error, that we 
simply avoid the difficulty for now, especially since type 3 fu'ivla are 
good enough for everyone except Pierre %^).

The classic example of this problem is the brivla "iglu". JCB and Nora 
went back and forth for years over whether it was a valid fu'ivla in TLI 
Loglan and never reached an agreement - but then JCB in his later years 
wasn't as committed to audiovisual isomorphism as he was in 1960. (I'll 
let someone else look in the archives to see where iglu ended up in Lojban 
- I never can remember and Nora has gone to sleep). We adopted the type 3 
fu'ivla form because we WERE able to satisfy ourselves that it always gave 
a valid fu'ivla, and we are almost as confident about the special 
experimental fu'ivla "gismu" mentioned in the book, even though we spent 
only a short time checking it. But no one has solved the general case for 
the validity of a type 4 fu'ivla form and it has not been a priority, since 
such words are by definition barely part of the language in the first place.

>furthurmore, can it be proven within reasonable limits, such as not
>allowing fu'ivla?

I'm not sure what this means. There is no doubt that the algorithm could 
be mathematically proven by someone with the skills to do so - the proof 
complexity might be akin to the proof of the 4-color map theorem of 
topology though (I think that ran several hundred pages) - it is a simple 
problem with a very bushy tree.

It is probably easier to come up with a definitive test for whether a word 
is a valid fu'ivla, given some maximum length to test, but no one has done 
so because the test isn't worth much. The critical point of fu'ivla will 
be nonce usage when you want to communicate a new concept that has not been 
analyzed, and we don't believe that it is possible to have human algorithm 
for making fu'ivla of arbitrary form. If you always have to test fu'ivla 
against a computer program, then adding fu'ivla will tend to be a "Lojban 
academy" function, and right now there is little sentiment to create such 
an academy, even without all the mutterings about "Cabals" and "Lojban 
Central".

lojbab
--
lojbab [email-masked]
Bob LeChevalier, President, The Logical Language Group, Inc.
2904 Beau Lane, Fairfax VA 22031-1303 USA 703-385-0273
Artificial language Loglan/Lojban: http://www.lojban.org