TENSE

TODO add ungrammatical items to the test suite

Yiddish has three tenses, past, present and future. Present tense is
indicated through the use of a simple VP (ie no AUX) with the main
verb being inflected to agree with the subject for number and person
-- the agreement paradigm is presented under the agreement
section. Both past and future tenses are indicated through the use of
AUX + verb constructions. In the past tense, the auxiliary is the
finite form of one of the verbs hobn (to have) and (to be) -- which
again agree with the subject -- which combines with the past particle
of the matrix verb. The past participle is formed by adding the suffix
-e or -n to the verb, and depending on the verb, a prefix ge-.  [TODO
when g- ??]. The auxiliary used is selected for by the verb with hobn
being more frequent, and zayn tending to be selected by verbs which
indicate whole body movement, body state, or motion. The past tense
construction is illustrated below:

Source: {a:217}
Vetted: t
Judgment: g
Phenomena: {tam}
Ikh hob geshribn.
Ikh hob ge-shrayb-n.
1SG.NOM have;1SG PP-write-PP.
I have written.

Source: {a:217}
Vetted: t
Judgment: g
Phenomena: {tam}
Ikh bin geblibn.
Ikh bin ge-blayb-n.
1SG.NOM be;1SG PP-remain-PP.
I remained.

These show incorrect selection of hobn and zayn as auxiliaries and
incorrect agreement on the auxiliaries:

# Wrong auxiliary used
Source: author based on {a:217}
Vetted: t
Judgment: u
Phenomena: {tam}
Ikh bin geshribn.
Ikh bin ge-shrayb-n.
1SG.NOM have;1SG PP-write-PP.
I have written.

# Wrong auxiliary used
Source: author based on {a:217}
Vetted: t
Judgment: u
Phenomena: {tam}
Ikh hob geblibn.
Ikh hob ge-blayb-n.
1SG.NOM be;1SG PP-remain-PP.
I remained.

# Wrong form of the auxiliary
Source: author based on {a:217}
Vetted: t
Judgment: u
Phenomena: {agreement}
Ikh hot geshribn.
Ikh ho ge-shrayb-n.
1SG.NOM have;3SG PP-write-PP.
I have written.

# Wrong form of the auxiliary
Source: author based on {a:217}
Vetted: t
Judgment: u
Phenomena: {agreement}
Ikh iz geblibn.
Ikh iz ge-blayb-n.
1SG.NOM be;3SG PP-remain-PP.
I remained.

Additionally, there are also some verbs which take hobn as an
auxiliary in the present tense. In these cases both verbs agree with
the subject:

Source: {a:217}
Vetted: t
Judgment: g
Phenomena: {tam}
Ikh hob lib.
Ikh hob lib.
1SG.NOM have;1SG like;1SG.
I liked.

These verbs also take gehat, the past participle of hobn in the past
tense:
 
Source: {a:217}
Vetted: t
Judgment: g
Phenomena: {tam}
Ikh hob lib gehat.
Ikh hob lib gehat.
1SG.NOM have;1SG like;1SG have;PP.
I liked.

The future tense is indicated through the finite form of the auxiliary
veln (will) + the infinitive form of the verb. This is illustrated
below:

Source: {a:218}
Vetted: t
Judgement: g
Phenomena: {tam}
Ikh vel shraybn.
Ikh vel shrayb-n.
1SG.NOM shall;1SG write-INF.
I shall write.

# Wrong conjugation of auxiliary
Source: author based on {a:218}
Vetted: t
Judgement: u
Phenomena: {tam}
Ikh velst shraybn.
Ikh vel-st shrayb-n.
1SG.NOM shall- write-INF.
I shall write.

We implemented tense thusly: 

Under the Tense, Aspect and Mood section of the questionnaire, the
default hierarchy of past, present and future was kept. Then under the
Syntax part of this section we expanded the form hierarchy by creating
the sub-type past-part, which inherits from finite.

For the tense constructions, three separate auxiliary types were
defined each for hobn, zayn, and veln, respectively. All of these were
specified to not contribute any predicate, since their function is
more grammatical, indicating tense. They also make the auxiliary's
form finite, and in the case of hobn and zayn, they specified the
tense of the auxiliary to be past, while zeln makes the auxiliary's
tense future. All were constrained such that the subject is an NP with
the case selected by the verbal complement. Hobn and zayn constrain
the complement's form to be past-part as per the past tense
construction, while veln constrains its to be nonfinite, as per the
future tense construction. We then inserted all the various inflected
forms of the auxiliaries into the relevant spelling fields. Since no
person/number constraints can be applied to these, these will
overgenerate (as discussed in the final section).

As the first two auxiliaries are both used in the same AUX +
past-participle construction to indicate the past tense, these two
auxiliary types were constrained in exactly the same way, however we
chose to keep them separate so that later on they can be selected for
by specific verbs (this limitation of the customization is also
discussed in the final section).

In order to derive the infinitive and past-participle forms of the
verb, we created new inflecting lex rules. We already had an
obligatory suffix position class (which now had to be excluded from
applying to auxiliaries) set up for finite present tense verbs, which
agree with person and number (the forms are: zero, -st, -t, -en,
-n). Since both the past participle and the infinitive form are also
indicated through a suffix attaching to the root (which both happen to
be either -e or -en), and these forms are all mutually exclusive, the
same position class was used for all three, with separate lex rules
set up for infinitive and past particple suffixes that have the same
suffixes but apply the relevant form constraint to the verb. It's not
hopelessly ambiguous though, as the past participle often takes the
prefix ge-, which was added through a prefix position class with an
inflecting lex rule and was also constrained so that the verb has past
participle form. 

Our grammar then appears to leave an ambiguous gap, where the verb has
a -n or -en suffix that is ambiguous between infinitive and past
participle interpretation when prefix ge- does not occur. This does
not occur all that often in Yiddish however, as the past participle
often -- but not always -- involves vowel mutation of the root (which
our morphological analyzer 'undoes').

TODO example?

We currently do not handle periphrastic verbs which take the AUX hobn
in the present tense (Ikh hob lib.) -- nor the past tense construction
of these verbs either. This could easily be modeled as an auxiliary
type, however, once again, the matrix does not support specific verbs
selecting specific auxiliaries, so we have for now left this
unimplemented.


ASPECT

Yiddish has a number of aspects, including (but not limited to)
perfective, inchoative, iterative, habitual, and singulative. We
focused on the perfective, habitual and inchoative aspects for this
lab.

The  

We also created inflection lex rules which straightforwardly handle
the on-, der-, far-, oys, op- prefixes that indicate perfective
aspect. However it should be noted that it looks like this is a bit of
a hack as these prefixes are selected for by the verb, being perhaps
best analyzed as verb particles that can attach enclitically to the
left of the verb depending on dialect. We have opted to implement them
as prefixes since the Grammar Matrix cannot handle verb particles, as
discussed in the final section.

The inchoative aspect.

The habitual aspect.
