Developing a German grammar for analysis and generation using OpenCCG

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Developing a German grammar for analysis and
generation using OpenCCG

• Ciprian Gerstenberger
• University of Saarland
• IGK Colloquium January 13th 2005

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Outline

1. NLP environments a comparison
2. The choice OpenCCG
3. The formalism MMCCG
4. The German grammar
5. Future work

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Dialogue systems

• building dialogue systems ? linguistic resources
• linguistic resources ? tools for developing and
  maintaining
• wide range of different NLP environments
• ? Which is the most appropriate environment for
  our purposes?

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NLP environments for dialogue systems

• General requirements
• both for analysis and generation
• multi-lingual
• easy domain reconfigurability
• Requirements for NLG
• realization of contextually sensitive utterances
• linguistically motivated control over flexible
  sentence realization

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NLP environments for dialogue systems

• Technical requirements
• freely available
• well documented
• offering support when needed
• freely available resources (for German)
• efficient
• platform independent

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NLP environments

• KPML (Lisp) Systemic-Functional Grammar (SFG)
• OpenCCG (Java) Multi-Modal Combinatory
  Categorial Grammar (MMCCG)
• Babel (Prolog) Head-Driven Phrase Structure
  Grammar (HPSG)
• LKB (Lisp) Head-Driven Phrase Structure Grammar
  (HPSG)
• XLE (C) Lexical Functional Grammar (LFG)
• XTAG (Lisp) Tree Adjoning Grammar (TAG)
• XDG (Oz) Topological Dependency Grammar (TDG)

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NLP environments Babel

• Babel-System (S. Müller)
• implementing HPSG
• Prolog
• only analysis, no generation
• multi-lingual (?)
• resources for German grammar with good coverage
• freely available
• documentation
• support (?)

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NLP environments LKB

• LKB
• implementing HPSG
• Lisp
• multi-lingual
• both analysis and generation
• but resources for German not usable for
  generation
• freely available
• documentation
• support (?)

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NLP environments XTAG

• XTAG
• implementing TAG
• Lisp
• both analysis and generation
• multi-lingual
• resources for German (DFKI ?)
• freely available
• documentation
• support (?)

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NLP environments XDG

• XDG
• implementing TDG
• Oz
• only analysis (generation as dependency parsing
  using TAGs)
• multi-lingual (?)
• resources for German (toy grammars)
• freely available
• documentation (?)
• support

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NLP environments KPML

• KOMET-Penman Multilingual Linguistic resource
  development
• implementing Systemic-Functional Grammar (SFG)
• Lisp
• multi-lingual
• flexible generation
• good sentence realization control
• only for generation, no parsing
• resources for German grammar with good coverage
• freely available
• documentation and support

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NLP environments XLE

• Xerox Linguistic Environment
• implementing LFG
• C and Tcl/Tk
• multi-lingual
• both analysis and generation
• resources for German (not freely available)
• documentation
• support
• not freely available

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NLP environments OpenCCG

• OpenCCG
• implementing Multi-Modal Combinatory Categorial
  Grammar (MMCCG)
• open source Java-based NLP library
• both analysis and generation
• multi-lingual
• no resources for German, but grammars for English
• freely available
• documentation
• support

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NLP environments The Choice

• OpenCCG
• Java-based NLP library ? platform independent
• analysis and generation ? uniform grammar
  resources
• multi-lingual ? extendable
• used and in use in several other projects
  FLIGHTS, COMIC, COSY
• supporting output format for TTS (e.g. APML)
• optimized sentence realization
• flexible generation
• sentence realization control

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Basic formalism CCG

• Combinatory Categorial Grammar
• lexicalized grammar formalism
• lexical items are assigned syntactic categories
• combinatory rules

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MMCCG

• Multi-Modal Combinatory Categorial Grammar
• refining CCG by introducing means of controlling
  the application of combinatory rules
• specifying modes on category forming operators
  (slashes)
• making application of rules dependent on the
  slash mode
• four basic modes governing different levels of
  associativity and permutativity

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Example

• Der Hund sieht die Katze.

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Example (cont.)

• Der Hund sieht die Katze.

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Developing a German Grammar

• joint work with Magdalena Wolska (DIALOG Project)
• Desiderata
• uniform resources for analysis and generation
• covering all phenomena in our domains
• achieve more generality of the grammar than wrt
  phenomena encountered in our (relatively small)
  corpora

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Phenomena

• Some phenomena in German
• agreement
• position of the finite verb
• Topological Fields controlling the Vorfeld
• complex sentences
• ambiguity
• controlling sentence realization

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Lexical forms

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Agreement

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Agreement (cont.)

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Agreement/Complex sentences

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Clause types

• Verb-initial clauses
• yes/no questions
• Soll ich die den Titel zu der Liste hinzufügen?
• alternative questions
• Möchtest Du Mozart oder Bach hören?
• imperatives
• Wähle das Album Californication von den Red Hot
  Chili Peppers!

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Clause types (cont.)

• Verb-second clauses
• main declarative
• Der Titel wurde hinzugefügt.
• wh-question
• Welcher Künstler spielt Missunderstood?

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Clause types (cont.)

• Verb-final clauses
• subordinate clause
• Wenn Sie möchten, kann ich We Just Cant Get
  Enough CCG abspielen.
• relative clause
• Ich nehme aus den ersten vier Alben, die du hast,
  jeweils den ersten Song.
• complement clause
• Ich glaube, daß das Album Dangerously In Love
  heißt.

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Topological Fields
Controlling the Vorfeld occupation using flags
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Topological Fields (cont.)
Controlling the Vorfeld occupation using flags
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Analysis Ambiguities
Der Hund von dem traurigen Mann den ich sah
rennt.
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Analysis Ambiguities (cont.)
Das Kind rennt wenn der Hund rennt weil die Katze
rennt.
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Generation

• Sentence realization without control

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Generation (cont.)

• Sentence realization with control fronted
  subject

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Generation (cont.)

• Sentence realization with control fronted object

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Future Work (1)

• extending the grammar wrt the two domain
  currently modelled (MP3 and maths tutorial)
• (AP, NP, sentence, etc.) coordination
• complex NP (e.g. postmodifications)
• control and raising verbs
• particle verbs (Ich spiele den Song ab vs. Ich
  möchte den Song abspielen)
• Topological Fields scrambling in the Mittelfeld

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Future Work (2)

• analysis coping with partial input, ill-formed
  utterances
• generation realizing elliptical output
• using a dynamic morphological module
• development of an ontology