[developers] Paraphrase grammars and SEMI's

[Berthold Crysmann]

On Mon, 2009-05-25 at 21:59 +0900, Francis Bond wrote:
> G'day,
> 
>    we would like to solicit opinions (especially from Dan) about the
> following question:
> 
> If you are making a paraphrase grammar, should it use the language
> internal MRS, or the post SEM-I external MRS.
> 
> That is:
> 
> Internal: TEXT - ERG - MRS -　EnEn - MRS - ERG - TEXT
> or
> External: TEXT -ERG - MRS - MRS' - EnEn - MRS' - MRS - ERG - TEXT
> 
> 
> My view is that we should use the external MRS for the following reasons:

Seconded. 

We did some paraphrasing with GG in Checkpoint. At that time, the
paraphraser was using the internal MRS. As a result, I had to
cross-classify internal and external semantic semantic entities, such
that the types in mtr.tdl were compatible with both universes. The
result is not a beauty. 

B

> (i) the SEM-I is the interface to outside resources, such as WordNet,
> which we plan to mine for rules
> (ii) the internal MRS is more likely to change without warning
> (iii) current MT systems all use the internal rules
> 
> However, there are also reasons for choosing the internal MRS
> (i) full access to the grammar internals
> (ii) the current paraphrasing rules use the internal MRS
> (iii) two fewer steps to pass through
> 
> Using the external MRS also means that the internal hierarchy is
> obscured.  To pick a not at all random example, we want to under
> specify B's A and (the) A of B.  This is easy to do in the current ERG
> due to two hierarchies:
> _the_q_rel := def_q_rel, _def_explicit_q_rel := def_q_rel
> _of_q_rel :=of_q_rel, poss_rel := of_q_rel.
> 
> By creating an MRS with def_q_rel and of_q_rel, both alternatives (and
> more) are generated.
> However, this is not obvious from the SEM-I, which only records what
> predicates are exposed, and says nothing about their place in the
> hierarchy.  It is also not encoded in predicates.erg.tdl, although
> perhaps it should be?  Currently (for the erg, rather than terg) it
> says:
> 
> poss_rel := predsort. (in predicates.tdl)
> _of_p_rel := of_p_rel. (in predicates.erg.tdl)
> def_explicit_q_rel := quant_rel. (in predicates.erg.tdl)
> _the_q_rel := quant_rel. (in predicates.erg.tdl)
> def_q_rel := quant_rel. (in predicates.tdl)
> 
> So, any thoughts?
> 
>