Grammatical Relations and Lexical Functional Grammar Formalisms Spring

Grammatical Relations and Lexical Functional Grammar Formalisms Spring Term 2004

Grammatical Relations • Subject – Sam ate a sandwich. – A sandwich was eaten by Sam. • Direct object – Sam ate a sandwich. – Sue gave Sam a book. – Sue gave a book to Sam. • Others that we will define later

Grammatical Relations in Grammar Formalisms • Tree Adjoining Grammar: – Subject is defined structurally: first NP daughter under S – Object is defined structurally: NP that is a sister to V – But TAG output can be mapped to a dependency grammar tree that includes subject and object. • Categorial Grammar: – Grammatical relations are defined structurally if at all. • Head Driven Phrase Structure Grammar: – Subject is defined indirectly as the first element on the verb’s subcategorization list. • Lexical Functional Grammar: – Grammatical relations are labelled explicitly in a feature structure.

Motivation for Grammatical Relations: Subject-Verb Agreement – – Sam likes sandwiches. *Sam like sandwiches. The boys like sandwiches. *The boys likes sandwiches. • Hypothesis 1: The verb agrees with the agent. • Hypothesis 2: The verb agrees with the first NP. • Hypothesis 3: The verb agrees with the NP that is a sister of VP. • Hypothesis 4: The verb agrees with the subject. – Vacuous unless we have a definition or test for subjecthood.

Checking the hypotheses • Hypothesis 1: – Can you think of a counterexample in English. ? • Hypothesis 2: – Can you think of a counterexample in English? – Can you think of a counterexample in another language that has subject-verb agreeement? • (not Japanese or Chinese)

Some differences between English and Warlpiri (Australia) S VP’ NP VP Aux The two small children are V NP chasing that dog. V NP S NP Wita-jarra-rlu Small-DU-ERG AUX NP NP ka-pala wajili-pi-nyi yalumpu kurdu-jarra-rlu maliki. pres-3 du. SUBJ chase-NPAST that. ABS child-DU-ERG dog. ABS

Some Definitions • Case marking: different word form depending on the grammatical relation: – – She ate a sandwich. (nominative case marking: subject) *Her ate a sandwich. Sam saw her. (accusative or objective case marking: object) *Sam saw she. • Ergative case marking: – Marks the subject, but only if the verb is transitive (has a direct object). • Absolutive case marking: – Marks the subject, but only if the verb is intransitive. – Also marks the direct object. • English has nominative and accusative case markers on pronouns. • English does not have ergative or absolutive case marking.

Possible word orders in Warlpiri that are not possible in English • *The two small are chasing that children dog. • *The two small are dog chasing that children. • *Chasing are the two small that dog children. • *That are children chasing the two small dog.

Checking the hypotheses • Hypothesis 2: – Does it work for Warlpiri? • Hypothesis 3: – Does it work for Warlpiri?

English and Warlpiri Under Hypothesis 3 S Deep structure VP’ NP VP Aux English V NP S Surface Structure VP’ NP VP Aux V NP

English and Warlpiri under Hypothesis 3 S VP’ VP NP Aux Warlpiri V Deep structure NP S AUX S S NP NP S Surface Structure VP’ NP VP Aux e ee V NP e

English and Warlpiri under Hypothesis 3 S VP’ VP NP Aux Warlpiri V S NP Deep structure NP Adjunctions: represent the real word order S AUX S S NP Remnants of the original tree represent gramamtical relations NP S VP’ NP VP Aux e ee V NP e Empty categories: represent semantic roles Surface Structure

English and Warlpiri under Hypothesis 4 English Constituent structure: represents word order and grouping of words into constituents S Subject VP’ NP VP Aux Warlpiri NP V V NP NP NP “two small children” Predicate chase agent theme Object “that dog” NP S Aux Functional structure: represents grammatical relations and semantic roles

English and Warlpiri under Hypothesis 4 English Constituent structure: represents word order and grouping of words into constituents S Subject VP’ NP VP Aux Warlpiri NP V chase agent theme Object “that dog” Mapping from c-structure to fstructure V NP NP NP “two small children” Predicate NP S Aux Functional structure: represents gramamtical relations and semantic roles

English and Warlpiri under Hypothesis 4 English Constituent structure: represents word order and grouping of words into constituents S Subject VP’ NP VP Aux V NP S Aux V NP NP NP “two small children” Predicate chase agent theme Object “that dog” NP Mapping from c-structure to f-structure Warlpiri Functional structure: represents gramamtical relations and semantic roles

Keeping Score Hypothesis 3: • One structure contains a mish-mash of word order, constituency, grammatical relations, and thematic roles • Adjunctions • Empty categories and invisible constituents Hypothesis 4: • Need an extra data structure for grammatical relations and semantic roles • Need a mapping between c-structure and f-structure • Need a reproducible, falsifiable definition of grammatical relations.

Levels of Representation in LFG [s [np The bear] [vp ate [np a sandwich]]] constituent structure Grammatical encoding SUBJ Agent Eat < agent SUBJ PRED eat SUBJ functional structure Lexical mapping thematic roles patient > lexical mapping OBJ S NP OBJ VP VP V NP OBJ V PP OBL Grammatical Encoding For English!!!

A surprise • Syntax is not about the form (phrase structure) of sentences. • It is about how strings of words are associated with their semantic roles. – Phrase structure is only part of the solution. • Sam saw Sue – Sam: perceiver – Sue: perceived

Surprise (continued) • Syntax is also about how to tell that two sentences are thematic paraphrases of each other (same phrases filling the same semantic roles). – It seems that Sam ate the sandwich. – It seems that the sandwich was eaten by Sam. – Sam seems to have eaten the sandwich. – The sandwich seems to have been eaten by Sam.

How to associate phrases with their semantic roles in LFG • Starting from a constituent structure tree: • Grammatical encoding tells you how to find the subject. – The bear is the subject. • Lexical mapping tells you what semantic role the subject has. – The subject is the agent. – Therefore, the bear is the agent.

Levels of Representation in LFG [s [np The sandwich ] [vp was eaten [pp by the bear]]] constituent structure Grammatical encoding SUBJ PRED OBL patient eat agent Eat < agent OBL patient > SUBJ lexical mapping SUBJ S NP functional structure Lexical mapping thematic roles VP VP V NP OBJ V PP OBL Grammatical Encoding For English!!!

Active and Passive • Active: – Patient is mapped to OBJ in lexical mapping. • Passive – Patient is mapped to SUBJ in lexical mapping. • Notice that the grammatical encodings are the same for active and passive sentences!!!

Passive mappings • Starting from the constituent structure tree. • The grammatical encoding tells you that the sandwich is the subject. • The lexical mapping tells you that the subject is the patient. – Therefore, the sandwich is the patient. • The grammatical encoding tells you that the bear is oblique. • The lexical mapping tells you that the oblique is the agent. – Therefore, the bear is the agent.

How you know that the active and passive have the same meaning • In both sentences, the mappings connect the bear to the agent role. • In both sentences, the mappings connect the sandwich to the patient role (roll? ) • In both sentences, the verb is eat.

Levels of Representation in LFG [s-bar [np what ] [s did [np the bear] eat ]] constituent structure Grammatical encoding OBJ SUBJ patient Eat < agent SUBJ S-bar NP S OBJ agent patient > PRED eat functional structure Lexical mapping thematic roles lexical mapping OBJ VP S NP SUBJ V PP OBL Grammatical Encoding For English!!!

Wh-question • Different grammatical encoding: – In this example, the OBJ is encoded as the NP immediately dominated by S-bar • Same lexical mappings are used for: – What did the bear eat? – The bear ate the sandwich.

Functional Structure SUBJ PRED TENSE OBJ PRED ‘bear’ NUM sg PERS 3 DEF + ‘eat< agent patient > SUBJ OBJ past PRED ‘sandwich’ NUM sg PERS 3 DEF -

Functional Structure • Pairs of attributes (features) and values – Attributes (in this example): SUBJ, PRED, OBJ, NUM, PERS, DEF, TENSE – Values: • Atomic: sg, past, +, etc. • Feature structure: [num sg, pred `bear’, def +, person 3] • Semantic form: ‘eat<subj ob>’, ‘bear’, ‘sandwich’

Semantic Forms • Why are they values of a feature called PRED? – In some approaches to semantics, even nouns like bear are predicates (function) that take one argument and returns true or false. – Bear(x) is true when the variable x is bound to a bear. – Bear(x) is false when x is not bound to a bear.

Why is it called a Functional Structure? X squared Each feature has a unique value. 1 1 2 4 3 9 Also, another term for grammtical relation is grammatical function. 4 16 5 25 features values

We will use the terms functional structure, f-structure and feature structure interchangeably.

Give a name to each function f 1 SUBJ PRED ‘bear’ NUM sg f 2 PERS 3 DEF + PRED ‘eat< agent patient > SUBJ OBJ TENSE past OBJ PRED ‘sandwich’ NUM sg f 3 PERS 3 DEF -

How to describe an f-structure • F 1(TENSE) = past – Function f 1 applied to TENSE gives the value past. • F 1(SUBJ) = [PRED ‘bear’, NUM sg, PERS 3, DEF +] • F 2(NUM) = sg

Descriptions can be true or false • F(a) = v – Is true if the feature-value pair [a v] is in f. – Is false if the feature-value pair [a v] is not in f.

This is the notation we really use • (f 1 TENSE) = past • Read it this way: f 1’s tense is past. • (f 1 SUBJ) = [PRED ‘bear’, NUM sg, PERS 3, DEF +] • (f 2 NUM) = sg

Chains of function application • (f 1 SUBJ) = f 2 • (f 2 NUM) = sg • ((f 1 SUBJ) NUM) = sg • Write it this way. (f 1 SUBJ NUM) = sg • Read it this way. “f 1’s subject’s number is sg. ”

More f-descriptions • (f a) = v – f is something that evaluates to a function. – a is something that evaluates to an attribute. – v is something that evaluates to a function, symbol, or semantic form. • (f 1 subj) = (f 1 xcomp subj) – Used for matrix coding as subject. A subject is shared by the main clause and the complement clause (xcomp). • (f 1 (f 6 case)) = f 6 – Used for obliques

SUBJ PRED S NP N TENSE VFORM XCOMP VP V VP-bar SUBJ OBL-loc COMP VP V PRED ‘lion’ NUM pl PERS 3 ‘seem < theme > SUBJ’ XCOMP pres fin SUBJ [ ] VFORM INF PRED ‘live< theme loc >’ PP P NP DET N Lions seem to live in the forest CASE PRED OBJ OBL-loc ‘in<OBJ>’ PRED ‘forest’ NUM sg PERS 3 DEF +

SUBJ f 1 f 2 PRED S n 1 n 2 NP n 3 N VP V n 5 TENSE VFORM XCOMP n 4 VP-bar SUBJ n 6 f 4 n 7 COMP VP V P n 11 OBL-loc n 8 PP n 9 PRED ‘lion’ NUM pl PERS 3 ‘seem < theme > SUBJ’ XCOMP pres fin SUBJ [ ] f 3 VFORM INF PRED ‘live< theme loc >’ f 5 n 10 NP DET n 14 N n 12 n 13 Lions seem to live in the forest CASE PRED OBJ f 6 OBL-loc OBJ OBL-loc ‘in<OBJ>’ PRED ‘forest’ NUM sg PERS 3 DEF +

SUBJ f 1 f 2 PRED S n 1 n 2 NP n 3 N VP V n 5 TENSE VFORM XCOMP n 4 VP-bar SUBJ n 6 f 4 n 7 COMP VP V P n 11 OBL-loc n 8 PP n 9 PRED ‘lion’ NUM pl PERS 3 ‘seem < theme > SUBJ’ XCOMP pres fin SUBJ [ ] f 3 VFORM INF PRED ‘live< theme loc >’ f 5 n 10 NP DET n 14 N n 12 n 13 Lions seem to live in the forest CASE PRED OBJ f 6 OBL-loc OBJ OBL-loc ‘in<OBJ>’ PRED ‘forest’ NUM sg PERS 3 DEF +