[developers] on generation failure with the Barcelona release and later

[Xuchen Yao]

Hi,

I noticed there was some intensive discussion of generation failure from 
unknown words in the mailing list last year. Then people agreed to 
continue the discussion at last year's meeting but I didn't find any 
memo on the delph-in website. It looks like the Barcelona (0907) ERG 
release was intended for this issue. So I switched from the current 
stable version (0902) to 0907 or even the newest in the trunk (1004) 
hoping to have a better handle of unknown words (or the "invalid 
predicates" error). But unfortunately it didn't work out. Here's a 
shortened observation from my experiment:

The basic idea is to follow what Stephan said:

"hence i think one would have to add an MRS post-processing step before 
trying to feed these MRSs back into the generator." from 
http://lists.delph-in.net/archive/developers/2009/001217.html

1. For unknown NNP, I changed `named_unk_rel' to `named_rel', it works 
for 0902. (If i remembered correctly, this change doesn't work for 0907 
and 1004).

2. For errors like invalid predicates: |basic_yofc_rel("1998"), from the 
sentence "He left in 1998." I changed basic_yofc_rel to number_q_rel =q 
card_rel as a shortcut to avoid a generation failure. This works under 0902.

3. For errors like invalid predicates: |"_iconic_jj_rel"|, from "This is 
an iconic place." I tried change the *_jj_rel to generic_unk_adj_rel 
with "iconic" as the CARG value. But this didn't work under both 0902 
and 0907.

I didn't observe generation failure on unknown verbs, but did have some 
cases of failure on nouns, such as: invalid predicates: 
|"_wreckage_nn_rel"|, |"_oscillation_nn_rel"|, |"_axiom_nn_rel"|.

For the generation task, my naive thought is that if cheap can parse a 
sentence, then LKB should generate from cheap's MRS output. For a 
successful parsing, I used the chart-mapping branch of cheap to support 
pre-processed (POS-tagged) sentences, but the problem of generation 
failure due to invalid predicates still exists. Since there was a 
discussion on this at last year's meeting and the ERG release is rolling 
forward, it looks to me this issue has already been solved (since the 
0907 release) but only I was using the wrong method. I'd appreciate it 
very much if somebody can help me out. Thanks.

With kind regards,

Xuchen Yao