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 L01 CPG: Postpositions & karaka mapping


     Grammar for Indian Languages

Properties of Indian langauges:

-  Relatively free word order 

-  Rich system of case endings and post position markers

-  Shared constructions, vocabulory, conventions etc.

No suitable existing computational grammar formalism. 
---------------------
   Postposition/Case Important

Postpositions or case important in
determining semantic roles (who-gave-what-to-whom).

- In Hindi: postpositions:  -ne, -ko etc. 
- In Telugu: case-endings:  -uDu (in rAmuDu)


Hindi examples:

- laDake ne  laDakI  ko phUla    diyA.
   (boy -ne  girl   -ko flower -0 gave)
  The boy gave a flower to the girl.

Relatively free word order:

- laDakI ko laDake ne phUla diyA.
- phUla laDake ne laDakI ko diyA.
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  Vibhakti to Karaka Mapping

For verb 'de' (give)::

Vibhakti:  Karaka role
- ne: karta      (like agent thematic role)
- ko: sampradana (like beneficiary)
- 0:  karma      (like patient)

Above is called KARAKA CHART
--------------------- 
 Problem: Above Mapping Does Not Work

- laDakA  laDakI ko phUla    de  rahA  hE
   (boy-0 girl  -ko flower-0 give -ing is
  The boy is giving a flower to the girl.

- laDake ko phUla denA paDA
                  (give had-to)
  The boy had to give a flower.

- laDake se phUla diyA nahIM gayA
                  (give not   could)
  The boy could not give the flower.
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   Solving Problem: Vital Observations

- Mapping depends on:
   * Verbal ending or verbal vibhakti
   * Also called TAM - tense-aspect-modality

+ Ex.: laDake ko phUla denA paDA
              --         -------
   * When TAM is 'nA_paDA', karta is marked by 'ko'

+ Ex.: laDake se phUla diyA gayA
                 --         -------
   * When TAM is 'yA_gayA', karta is marked by 'se'
      
- Mapping changes in systamatic ways when verbal ending
  or TAM changes. That is:
   * For all verbs, TAM 'nA_paDA' makes karta vibhakti to 'ko'
   * For all verbs, TAM 'yA_gayA' makes karta vibhakti to 'se'

+ Try with example verbs: dekhA (saw), piyA (drink)
---------------------------
    Framing a Linguistic Rule

- Choose one TAM as base (say, habitual present)
   * Give the karaka chart for the verb class

- Give rules for changing the karaka chart
  for other TAMs (verbal endings)
   * Karaka chart transformation
---------------------------
 Base Karaka Chart for a Verbal Root

Karaka chart for a verbal root:

Specify for the chosen ending (habitual past) the following:
- mandatory and optional karakas
- vibhakti associated with resp. nominals

For a different verbal ending (different TAM):
o  basic karaka chart is transformed
o  depending on the verb-form
----------------------------
 Mapping between Vibhakti & Karaka Level

Karaka chart for de[tA] (give[habit.])

  karaka     necessity   vibhakti

- karta     mandatory(m)   0
- karma        m           0
- sampradan    m           ko
- karana      opt          se
--------------------------
  Karaka Chart Transformation

Based on TAM (tense-aspect-modality) labels

TAM label   karaka chart transformation 

+ _yA         karta.vibhakti:= ne
+ _na_paDA    karta.vibhakti:= ko
+ _yA_gayA    karta.vibhakti:= se

The transformation is:
- independent of verbal root
- depends on TAM only
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