of 25/25
05/07/22 1 Rajat Kumar Mohanty AN INTRODUCTION TO TREE ADJOINING GRAMMAR
• date post

24-Feb-2016
• Category

Documents

• view

38

1

TAGS:

• auxiliary treesyesterday

Embed Size (px)

description

Rajat Kumar Mohanty. AN INTRODUCTION TO TREE ADJOINING GRAMMAR. OUTLINE. XTAG System Basics of TAG Formalism Operations Constraints Tree Families Feature Structure. 2. XTAG SYSTEM. What does it do? It takes a sentence as input, and provides: Constituency (NP, VP, PP, etc.) - PowerPoint PPT Presentation

Transcript of Rajat Kumar Mohanty

• Rajat Kumar MohantyAN INTRODUCTION TOTREE ADJOINING GRAMMAR

• OUTLINEXTAG SystemBasics of TAG FormalismOperationsConstraintsTree FamiliesFeature Structure

• 2. XTAG SYSTEMWhat does it do?It takes a sentence as input, and provides:Constituency (NP, VP, PP, etc.) Derivational History (how phrases are combined)Predicate/ Argument Structure (main verb, subject, object, etc)

• XTAG System: An OverviewInput SentenceMorph AnalyzerPOS TaggerPOS BlenderDerivation Structure

Morph DBTrees DBSyn DBTree SelectionTree GraftingSource: The XTAG Research Group, 2001Stat. DB

• Diverse Linguistic ResourcesSubcategorization information (argument structure)Syntax of various constructions (specific transformations)Frequency informationMorphological information

• A Tree Adjoining Grammar (TAG) consists of a quintuple (, NT, I, A, S) is a finite set of terminal symbols;NT is a finite set of non-terminal symbols: NT = ;S is a distinguished non-terminal symbol: S NT;I is a set of finite trees, called initial trees;A is a finite set of finite trees, called auxiliary trees.

• I: Initial TreeSlike NP0 VP

VNP1

like

• A: Auxiliary TreeSyesterday

yesterday

• Operations in Tree Adjoining GrammarSubstitutionThe substitution operation appends one tree at a frontier node of another tree. That is substitution takes place at non-terminal nodes on the frontier side, which are marked for substitution by a down arrow.

• Substitution S saw

NP0 VP

V NP1

sawNP John N

John

NP Mary N

Mary

S NP0 VP

V NP1 N N

John saw Mary

• AdjunctionThe adjunction operation is more powerful.It can be used to insert one tree within another.A new tree is built from an auxiliary tree and a tree ( : initial, auxiliary or derived) by adjunction.

NP0 VP

V NP1

bought S NP0 VP

V VP hasV NP1 bought has

VP

V VP*

has

• Derivation in Tree Adjoining GrammarDerived Tree

Derivation Tree

• Derived Tree in TAG S

NP0VPNV NP1 N Yesterday John saw Mary

• Derivation Tree in TAGsaw

John (1)Mary (2.2) yesterday (0)

• Declarative Intransitive Tree Family [Tnx0V]Sr [ ] nx0V [ ]

NP0 [ ] VP [ ] [ ] V< > The intransitive verbs (e.g., sleep, dance, etc. )select this Tree family [Tnx0V].

• Ergative Tree Family [TEnx1V]Sr [ ] nx1V [ ]NP1 [ ] VP [ ] [ ] V< > The ergative verbs (e.g., sink, melt, etc. )select this Tree family [Tnx1V].

• Declarative Transitive Tree Family [Tnx0Vnx1] Sr [ ] nx0Vnx1 [ ]

NP0[] VP [ ] [ ]

V< > NP1 [ ]The transitive verbs (e.g., eat, like, hit, etc. )select this Tree family [Tnx0Vnx1]. e.g., I ate an apple.

• Declarative Ditransitive Tree Family [Tnx0Vnx1pnx2]Sr [ ] nx0Vnx1pnx1 [ ] NP0 [ ] VP [ ] [ ] V< > NP1 [ ] PP2 [ ] The di-transitive verbs (e.g., put, usher, etc. )select this Tree family [Tnx0Vpnx1]. e.g.,The secretary ushered me into his office.

• Transitive Tree with Object NP Extraction [Wnx1nx0Vnx1] This problem, I solved. St [ ] [ ]

NP1 [ ] Sr [ ] [ ] NP0 [ ] VP[ ] [ ]

V< > NP1 [ ] NA

• Transitive Tree with object Wh-NP Extraction [Wnx1nx0Vnx1] What did he eat? Sq [ ] [ ]

NP1 [ ] Sr [ ] [ ] NP0 [ ] VP[ ] [ ]

V< > NP1 [ ] NA

• Sentential Complement Tree: [Tnx0Vnx1s2] S r [ ] nx0Vnx1s2 [ ]

NP0[ ] VP [ ] [ ]

V NP1[ ] S2*[ ] John told Mary that it was his turn.John begged Mary to increase his disk quota.

• Complementizer Tree: [sCOMP] Sc [ ] comp: mode: ind / inf COMP [comp: ]Sr* [assign-comp: ] [comp: ]mode: comp: nil assign-comp: John told Mary that it was his turn.John begged Mary to increase his disk quota.

• Suggested ReadingsJoshi, A. K. 1987. An Introduction to Tree Adjoining Grammars. In A. Manaster-Ramer, ed., Mathematics of Language. Amsterdam: John Benjamins.XTAG Research Group. 1999. A Lexicalized Tree Adjoining Grammar for English. Technical Report IRCS, University of Pennsylvania, Philadelphia.