[developers] Dropped arguments in DMRS

[Emily M. Bender]

Dear all,

Sorry to be late to the party.  I don't think there's much to add, but just
in case
it's helpful, here's a brief summary of the kinds of cases I know about
from the
Matrix grammarium:

(1) English loves its pronouns.  Many other languages used dropped arguments
where English would put in a pronoun --- this can be specific to certain
positions
(e.g. subjects in Spanish) or independent of argument position (e.g. rampant
pro-drop in Japanese).  Sometimes only certain persons/numbers are droppable
or there can be other constraints.  The argument optionality library in the
Matrix
was developed by Safiyyah Saleem, and is written up in these publications:

Saleem, Safiyyah. 2010. Argument Optionality: A New Library for the Grammar
Matrix Customization System. Masters thesis, University of Washington.
Safiyyah Saleem and Emily M. Bender. 2010. Argument Optionality in the
LinGO Grammar Matrix. Coling 2010: Posters. pp.1068-1076.
http://moin.delph-in.net/MatrixDoc/ArgumentOptionality

(2) As Mike and others have noted, dropped arguments can participate in
control
relations.  The tabe-sugiru `overeat' example isn't great (because Jacy
probably has the
wrong representation of sugiru), but it's easy to construct other examples,
such
as tabe-tai `[subject] wants to eat', and I'm sure the Spanish translation
of such a
sentence would have the same property. For non-subject arguments we could
get such a reentrancy in the case of causatives `tabe-saseru' `x causes y
to eat'.

(2') Depending on the representation of honorifics (as pointed out by
Mike), they
might also fit in under this heading.

(2'') While we're at, there are information structural constraints about
dropped
arguments (you can't drop focus), so we might have reason to posit an
info-str type
ICONS for them.  (I think Sanghoun discusses this in his thesis).

(3) We also see variable properties of dropped arguments recorded in the
morphology
in many languages --- Spanish subject agreement is a familiar example here,
but
we also see it for non-subject arguments in Zulu, Wambaya, Basque and many
others.
If we're worrying about coreference chains, I think we'd want to include
these.

(3') Another kind of variable property to consider is markers of
definiteness/discourse
status.  These are typically associated with the NP directly (choice of
article as in English,
inflection on the head noun as in Scandinavian languages, presence v.
absence of
an accusative case marker in I think Turkish and Farsi), and so wouldn't be
apparent
in the case of dropped arguments, but it may be possible to find cases
where the mark
is on the verb or on another argument.

(4) Trying to extrapolate Fillmore's work on definite/indefinite null
instantiation to
languages like Japanese, my guess is that if there is generally available
(definite)
pro-drop, but that particular predicates might also licenses indefinite
null instantiation,
at least for non-subject arguments. Such that `tabeta' in Japanese could
mean either
`You know who ate you know what' or `You know who ate something, but I
don't expect
you to know what.'  I haven't been able to substantiate this, though.

Possibly relevant (and possibly just naive) is this paper:
Bender, Emily M. and David Goss-Grubbs. 2008. Semantic Representations of
Syntactically Marked Discourse Status in Crosslinguistic Perspective. In
Proceedings of STEP 2008. College Publications.

(5) In Wambaya on variation on dropped arguments is arguments realized
solely
by modifiers.  Many of the examples involve numerals as the modifiers, so
that's
maybe less interesting, but here is a more interesting example (from
Nordlinger, 1998):

(4-158) Wurrudbanyi ngiy-a maganja murlu-ngunya-ni.
 pull 3.SG.NM.A-PST digging.stick.IV(ACC) eye-PROP.II-LOC
 The one that could see got the yam stick.

The suffix glossed PROP is a proprietive suffix which takes a noun and
derives
a modifier meaning `having (noun)'.  So here 'having eyes' means 'can see'.
II is a gender marker agreeing with the unexpressed subject. -LOC
is the case marker (actually ergative) indicating that this is a modifier
of the agent argument of the verb (pull).

Regarding tests, some ideas, though I'm not sure these are what you're
looking
for:

 * Trying to question the dropped argument:

(ia) I already ate.
(ib) What? (meaning what did you eat)

(ii) I already dined.
(iib) #What? (meaning what did you dine on)

Maybe this distinguishes dropped arguments from things that must be there
in the real world but aren't ever licensed as arguments?

 * Using the dropped argument to refer back to a salient element
in the discourse:

(iiia) What happened to the cake?
(iiib) #Kim ate.

Whereas I think this would work fine in Japanese.  Maybe that's because
that's
a pronoun-type dropped argument in Japanese?

... gotta go run and make some slides.

Emily




On Tue, Jan 12, 2016 at 11:38 AM, Ann Copestake <aac10 at cl.cam.ac.uk> wrote:

> Thanks!
>
> I assume that the unexpressed argument cases like English `eat' are
> different from dropped arguments in Spanish (and I guess Japanese)  because
> these apply across the board rather than being lexically specific.  I also
> assume it's clearer to a naive speaker that something is `missing'.    But
> I assume that putting back zero-pronouns just for the case where there's a
> coindexation is not something that one would want to try and do in a
> grammar - it doesn't seem likely it could be done compositionally and
> monotonically, if it could be done at all.
>
> Anyway, I will leave it up to others to decide what they want to do, but
> let's leave it that I am willing to try and add support directly in DMRS if
> that's thought to be helpful.
>
> All best,
>
> Ann
>
>
> On 12/01/2016 01:43, Michael Wayne Goodman wrote:
>
> I think we're all in agreement that the reduced clutter of DMRS and EDS is
> a good thing. I brought up the ICONS and coindexed-dropped-arguments issues
> as examples where the dependency representations are currently unable to be
> equivalent with existing MRS representations, but I think we'd all agree
> that we shouldn't just do whatever it takes to make them equivalent. More
> below...
>
> On Mon, Jan 11, 2016 at 1:22 PM Ann Copestake <aac10 at cl.cam.ac.uk> wrote:
>
>> Hi all,
>>
>> On 11/01/2016 16:41, Stephan Oepen wrote:
>> > if we were to add code to synthesize nodes for variables that are not
>> > introduced as the distinguished (or characteristic) variable of any EP
>> > but occur at least twice in an MRS, it would seem natural to me to
>> > leave these nodes unlabeled (they will not have characterization or
>> > other surface links either). this would also indicate that they have a
>> > somewhat different status formally (at least in terms of
>> > correspondences to a full MRS).
>>
>> we can't really leave them unlabelled in DMRS because they wouldn't show
>> up very well ...  From my perspective, the alternatives to changing the
>> DMRS code to allow them are 1. put zero pronouns back into JACY (without
>> quantifiers) 2. add zero pronouns in some sort of post-processing step
>> 3. add them to DMRS.  Mike mentioned ICONS - but it doesn't help here
>> because the nodes that would have to be equated don't exist.  Or, at
>> least, since ICONS can do absolutely anything, one could define a
>> variant of ICONS which did encode it properly, but it's really too much
>> of a stretch.
>
>
> In MRS, the ICONS solution might look like:
>
> RELS: < ... [ ... ARG1 i5 ...] [ ... ARG2 i6 ... ] ... >
> ICONS: < ... i5 equal i6 ... >
>
> where i5 and i6 are the dropped arguments that refer to the same thing
> (i.e., instead of coindexing the variable on both arguments). However,
> you're right that this would not naturally extend to DMRS, because it would
> require the relation to encode the rargname of both the source and target
> nodes. E.g., if we consider an extension to DMRS with <icons> as a sibling
> element to <node> and <link> elements:
>
> ...
> <icons>
>   <iarg1 nodeid="10001"><rargname>ARG1</rargname></iarg1>
>   <iarg2 nodeid="10002"><rargname>ARG2</rargname></iarg2>
>   <ireln>equal</ireln>
> </icons>
> ...
>
> I know. Yuck. Also, such graph would no longer be simple nodes and links,
> but instead nodes and links and icon-edges, which, at best, is harder to
> explain to DELPH-IN muggles. It also feels like we're just flailing about
> pretending to know nothing about the things we are equating.
>
> So I now agree that the simplest and most enticing solution is some kind
> of zero-pronoun, whether it's defined by the grammar (solutions (1) and
> (2)) or by the DMRS formalism itself (solution (3)). In addition, as you've
> mentioned, a zero-pronoun would helpfully contribute a nodeid that could be
> used for anaphoric pronouns in discourse, if that is something we'll need
> later.
>
> I believe the zero pronouns were dropped from Jacy precisely because of
> the clutter. Japanese drops a lot of arguments, and each one could result
> in two more uninteresting EPs (the zero pronoun and its quantifier). On a
> related note, my work on computing MRS isomorphism found that a major
> factor that caused inefficient computation was having many EPs with the
> same predicates (e.g., lots of udef_q_rels). Therefore, I don't think it's
> a great idea to reintroduce zero-pronouns in Jacy, unless we could
> constrain it somehow (e.g., only for coindexation, without quantifiers,
> etc.). I don't have strong arguments for choosing (2) or (3). With (2), it
> might be easier to insert variable properties on the zero-pronoun (e.g.
> evidenced from verb agreement, like the dropped subjects in Spanish or
> something), while (3) can help keep the representation consistent across
> grammars (since its defined by the formalism and not the grammar). (Aside:
> Japanese doesn't have verbal agreement in terms of PNG, but it does encode
> honorifics, even for dropped arguments. It would nice to keep this
> information for the zero pronouns somewhere.)
>
> Lastly, granting a nodeid for unexpressed arguments can help with other
> ICONS relations (i.e., of the information structure kind, not the
> variable-equating kind we were talking about before) where one of the
> participants is unexpressed.
>
> > i share your sentiment that the disappearing of unexpressed arguments
>> > in our dependency graphs in general reduces clutter and is desirable.
>> > co-indexation of such (unexpressed) variables admittedly challenges
>> > that position.  if we end up special-coding for these cases, it would
>> > be good to have the motivating examples and analyses readily available
>> > (and publicly vetted).  i believe emily may have been the first to
>> > argue for such co-indexation, probably from her work in the
>> > grammarium?
>>
>>
>> http://moin.delph-in.net/SingaporeMrsWellformedness
>>
>> the example Mike gave was tabe-sugiru = eat-exceed = overeat
>>
>> while it would be very good if someone could write this up or point us
>> to a proper write up, I don't think there's much room for argument about
>> needing it for Japanese, unless one uses zero pronouns
>>
>>
>> >
>> > —i recall we have talked once or twice in the past about adding an
>> > explicit distinction of unexpressed variables.  for the ERG at least,
>> > i believe dan (and others) often look at ‘u’ and ‘i’ (and maybe ‘p’)
>> > as varible sorts that indicate unexpressed arguments.  but that is at
>> > best a convention and prevents stronger typing of argument slots as
>> > would be desirable.  for example, the ARG2 of _eat_v_1 presumably must
>> > always be an ‘x’ when expressed, but dan abstains from putting that
>> > type into the lexical entry because the scoping machinery would
>> > complain at ‘x’-typed variable without a quantifier.
>> >
>> > would it work (and be desirable) to introduce a variable property, say
>> > [ XP bool ], to distinguish expressed from unexpressed roles?  i
>> > imagine it would not be hard to make all constructions that bind roles
>> > specialize XP to true; one could then use the VPM machinery upon MRS
>> > read-out to default remaining (unspecific) XP values to false.
>> > alternatively, i imagine one could obtain the same effect by making
>> > the hierarchy of variable types a little richer, i.e. put something
>> > above at least ‘x’ and ‘e’ to indicate unxpressed variants, say ‘w’
>> > and ‘d’ (the immediately preceding letters :-).
>> >
>> > any thoughts on actually introducing such an explicit marking of
>> > unexpressed arguments?
>> >
>> > all best, oe
>>
>> The problem with handling unexpressed arguments `properly' is that there
>> are multiple different classes of unexpressed arguments, as I outlined.
>> In some cases in the ERG, verbs with optional arguments have unexpressed
>> arguments in the semantics, while other cases don't.  This also
>> interacts with the desire to save on predicate names that has caused
>> many predicates to appear with different arities (which, of course,
>> isn't OK if one translates directly to a conventional logical
>> representation and has to be interpreted as some sort of notational
>> convenience).
>>
>> e.g., the ERG demo gives:
>>
>> Kim understood understand_v_by (e, x, p)
>>
>> Kim understood the sentence / Sandy understand_v_by (e, x, x')
>>
>> Kim understood that Sandy was scared understand_v_by (e, x, h, i)
>>
>> Kim ran run_v_1 (e, x)
>>
>> Kim ran the race   / the store run_v_1 (e, x, x')
>>
>> Kim hoped hope_v_1 (e, x)
>>
>> Kim dreamed dream_v_1 (e, x, p)
>>
>> I don't find this intuitive but we don't have a test set or criteria for
>> *MRS which would make it clear why one representation is to be preferred
>> over another, and I find it hard to imagine what such criteria could
>> be.  That's why I talked about anaphora in the previous message, since
>> that could have been an example of a clear cut difference, though it
>> seems (to me) it probably isn't.  Failing such criteria, I don't want to
>> argue that there's a problem with the ERG representations but it also
>> means that dropping them gives one less thing to worry about when we're
>> actually using the output.
>>
>> So - I don't think it'll be a big hassle to add them to the DMRS code,
>> but I don't propose to add them to the DMRS formal description and I
>> don't think it's worthwhile expending energy on trying to clean this
>> up.  There are ways to allow argument slot typing without messing up the
>> scope machinery, if that's something that needs to be fixed.
>>
>> All best,
>>
>> Ann
>>
>>
>>
>>
>>
>


-- 
Emily M. Bender
Professor, Department of Linguistics
Check out CLMS on facebook! http://www.facebook.com/uwclma
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