Semantics: Composition for Grammar Engineering | LING 567, Study notes of Linguistics

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Grammar Engineering

April 25, 2005

Semantics: Composition

Overview

Review: Anatomy of an MRS, relation, qeq

MRS in feature structures

• Composition:
• (^) ARGn • (^) HOOK, LKEYS (^) RELS and HCONS on mother nodes

(^) indices

ARGn

(^) handles

LBL

LBL

Building qeqs

Review: Anatomy of an MRS

• An MRS consists of:
• (^) A list of handle constraints • (^) A list of relations, each labeled by a handle (^) A top handle

(singly-rooted, connected, directed acyclic graphs).constraints can be resolved to form one or more treesAn (underspecified) MRS is well-formed iff the

Anatomy of a relation (1/2)

• A relation has: relation)being the event or individual introduced by the^ •^ One or more arguments: ARG0-n (ARG0 canonically^ •^ A label (handle)^ A predicate (string or type)

Anatomy of a handle constraint

Current sole handle constraint type:

(^) qeq

‘Equal modulo quantifiers’

Features: HARG, LARG

(^) Unless some quantifier scopes in between, the value

of this ARGn is the same as the label of that relation.

corresponds to a branch in an MRS tree.When the label of a relation is the value of an ARGn, this

relation.this corresponds to a ‘dotted’ branch – i.e., a dominanceWhen the value of an ARGn is qeq the label of a relation,

When else are handles identified?

scope.Relations with the same handle value share the same

their modifies.(adverbs, adjectives, PPs) which share their handles withTypically, we see this with intersective modifiers

RELS and HCONS on mother nodes

C-CONT of the mother.append of the values from the daughter(s) and theThe RELS and HCONS value of the mother is the

structure rules to introduce relations.C-CONT is the ‘constructional content’: allows phrase

Examples?

another daughter.From a semantic point of view, the C-CONT is just

Appending lists with unification

A (^) diff-list

(^) embeds an open-ended list into a container structure

A providing a ‘pointer’ to the end of the ordinary list.  LIST dlist 

^1   FIRST^ ne-list

item

REST

(^2) list  

LAST

2

  B  LIST dlist 

^3   FIRST^ ne-list

item

REST

(^4) list  

LAST

4

 

To append : (i) unify the front of

(^) B (i.e. the value of its LIST^

feature) into the tail of

(^) A (its LAST value) and^

(ii) use the tail of difference list

(^) B as the new tail for the result^

of the concatenation.

Matrix type: dl-append

Not (^) for direct use in the grammar: this type is just meant

as a reference.

dl-append

avm

& [APPARG1 [LIST

#first,

LAST #between],

APPARG

[LIST

#between,

LAST #last],

RESULT

[LIST

#first,

LAST #last]].

Diff-lists: practicalities

direct unification failure.Typically errors with diff-lists involve circularity and not

check your difference lists.If the LKB complains about circular feature structures,

Don’t try to constrain the length of a difference list.

relation can result in diff lists constrained to be empty.Unifying structures which include diff lists in an append

Semantic compositionality in action

basic-unary-phrase

:= phrase

[

SYNSEM.LOCAL.CONT [

RELS [

LAST #lastLIST #first,

]],

C-CONT

[

RELS

[ LIST #mid, LAST #last

]],

ARGS

sign

[ SYNSEM.LOCAL

[

CONT

[ RELS [

LAST #mid ]]]]>].LIST #first,

Now what

and HCONS from daughters.Phrase structure rules (and lexical rules) gather up RELS

RELS and HCONS.Phrase structure rules also (optionally) introduce further

the right things?How do we link the ARGn positions of the relations to

things?How do we link the HARG/LARG of qeqs to the right

HOOK (2/2)

C-CONT.HOOK.The HOOK of a sign is identified its with the

semantic head daughter, if there is one.The C-CONT.HOOK in turn is identified with the

C-CONT.HOOK need to be constrained appropriately.Otherwise, the LBL, INDEX, and XARG inside

LKEYS

LKEYS.KEYREL.relations on the RELS list, most notablyThe feature LKEYS houses pointers to important

Only appropriate for lexical items.

Serves as a uniform place to state linking constraints.

LKEYS.KEYREL.ARGn.HOOK.LBL of arguments/modifiees andLinking constraints: equality between HOOK.INDEX or