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Reference Resolution And Cognitive Grammar. Susanne Salmon-Alt Laurent Romary Loria - Nancy, France ICCS-01 San Sebastian, May 2001. General context. Computational objectives Designing man-machine dialogue systems with graphical user feedback and gestural designation - PowerPoint PPT Presentation
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Reference Resolution And
Cognitive Grammar
Susanne Salmon-AltLaurent Romary
Loria - Nancy, France
ICCS-01 San Sebastian, May 2001
General context
Computational objectives Designing man-machine dialogue systems with graphical user
feedback and gestural designation– Allowing the user to express himself spontaneously
Linguistic objectives Deriving a model that widely covers the range of possible
referring expressions and their use in context– Narrowing the discrepancy between computational models and
linguistic descriptions
Can a cognitive model be a means to achieve this?
Reference Resolution
Referring expressions
Contextmodel
“World”: perception and gestures
Interpretation
?
Evolution of the context
Take a big circle.
Okay, and now put a small lineon the left.
Don’t stick it to the circle.hearer puts a circle
on the screen...hearer puts a line
on the screen...
Reference Resolution
Associate referring expressions to identifying representations for contextual objects
C1 C2
C3
Reference Resolution
Take a big circle.
Okay, and now put a small lineon the left.
Don’t stick it to the circle.
{L2}
{C1} {L2}
{C1}
Referring expression Context model Referents
L1
L2 L3
The general background
Observations: reference in task-oriented dialogues – A wide variety of referring expressions: indefinites, definites,
demonstratives, pronouns– Both anaphoric and deictic uses
Modeling work is generally reduced to pronoun resolution– E.g. Centering (Grosz et al., 1995), Mitkov (1998)
Specificity of anaphoric expressions?– DRT / S-DRT: no essential difference between pronouns and
definites (linking as the main mechanism) How to integrate demonstratives (+gestures)?
Reference = Linking ?
Current strategies are basically co-referential– if indefinite : introduce a new discourse referent– if anaphoric : filter the context model on semantic
constraints and choose a suitable referent
Problems– empirically inappropriate for definites (Poesio &Vieira,
1998)– need of some additional mechanisms for...
Difficulties with Linking
Bridging
Take a triangle. Color the base in blue
one-anaphora
The green block supports the big pyramid, but not the red/small one.
ordinals andother-expressions
Take two lines. Move one line to the left.
Delete the other line.
visual information
Delete the triangle.
Need of cognitive structures rather than (or in complement to) of discourse variables
Cognitive Grammar (1)
Theoretical foundations (Langacker 1986, 1991)– language not self-contained, but part of cognitive
processing– speaker’s knowledge : inventory of symbolic units
(phonological and semantic pole)– semantic structures characterized relative to
presupposed « cognitive domains » (concepts, perceptual experiences, knowledge systems)
Cognitive Grammar (2)
Semantic structure of nouns
roof
Abstract schema:Delimitation of a region
in some domain
Instantiation:Profiling a sub-structure of one (ore more) presupposed domains
knife NOUN
Cognitive Grammar (3)
tr lm
horizontal
[ ON THE LEFT OF] [ THE LINE ON THE LEFT OF THE CIRCLE ]
Meaning (not truth-conditional): assembly and profiling of semantic units
Atemporal relation Assembly and profiling
[ LINE ] [ CIRCLE ]
Suitability
Interesting properties : interpretation of NPs– not linking, but profiling within a given domain
=> encompasses all kind of anaphoric expressions
– conceptual domains not primarily linguistic constructs => reference to percepual entities, gestures
– meaning = imposing a profile on a domain => prediction of preferred referential access :
The green block supports the big pyramid, but not the red/small one.
Problem : formalisation
The Model — Overview
abstract schema
for determiners
abstractschema
for nouns
complex schema for noun phrases
selected domain
restructured domain
context model
(domains)
Assembly of abstract schemas
Search for a suitable conceptual domain
Profiling of a regionof the domain
Calculus of an underspecified
domain
Unification with adomain of the context
model
Focusing an itemof a partition of the
domain
The Context Model (1)
Basic units : domains
@T1
Type = TRIANGLECard = 1Properties = {(size: big)}
@F1
Type = FIGURECard = 2Properties = {(size: small)}
Diff-Crit = Type
CIRCLE LINE
@C1 @L1
@C1
Type = CIRCLECard = 1
@L1
Type =LINECard = 1
The Context Model (2)
@F1
Type = FIGURECard = 2Properties = {(size: small)}
Diff-Crit = Type
CIRCLE LINE
@C1
@C1
Type = CIRCLECard = 1
@L1
Type =LINECard = 1
THE LINE ON THE LEFT OF THE CIRCLE
@L1
Grouping– Triggers
co-ordination prepositions argument structure perceptual criteria
– Result partitioned domain common type differentiation criterion focus structure
N
Underspecified Domains (1)
abstract schema
for determiners
abstractschema
for nouns
complex schema for noun phrases
Determiner semantics: grounding (how to locate the
thing within the given domain)
Noun semantics: delineate an item of a partitioned domain
Indefinite NPs « a N » (a line)
Noun semantics: delineate an item of type N within a domain
Determiner semantics: the item is located within a
domain of elements of type N
N N
Type = N
N
Underspecified Domains (2)
abstractschema
for nouns
abstract schema
for determiners complex
schema for noun phrases
Determiner semantics: grounding (how to locate the
thing within the given domain)
Noun semantics: delineate an item of a partitioned domain
Definite NPs « the N » (the line)
Noun semantics: delineate an item of type N within a domain
Determiner semantics: the item is located within a
domain of elements of a super-type of N
¬N ¬ N
Type > N
Underspecified Domains (3)
abstractschema
for nouns
abstract schema
for determiners complex
schema for noun phrases
Determiner semantics: grounding (how to locate the
thing within the given domain)
Noun semantics: delineate an item of a partitioned domain
Pronouns“it”
Pronoun semantics: delineate an item of a partitioned domain
Determiner semantics: Ø (the item has to be located from its focal position
focus)
Type = ?
Restructuration (1)
underspecified domain
selected domain
restructured domain
context model
(domains)
Profiling of a region in the domain
Focusing one item of the partition
Type = N
N N NN N N
Type = N
Indefinites « a N »
Restructuration (2)
underspecified domain
selected domain
restructured domain
context model
(domains)
Profiling of a region in the domain
Focusing item N of the partition
Type > N
N ¬ N ¬NN ¬N ¬N
Type > N
Definites “the N”
Restructuration (3)
underspecified domain
selected domain
restructured domain
context model
(domains)
Profiling of a region in the domain
No change
Type= ?
Pronouns « it »
Type = ?
Application - Example
Take a big circle.Okay, and now put a small line on the left.Don’t stick it to the circle.
Type = CIRCLEProp = BIG
@C
C4C3C2C1
Type = LINEProp = SMALL
@L
L4L3L2L1
Type = CIRCLE
@ ?
...
a big circle
Type = LINE
@ ?
...
a small line
Type = CIRCLEProp = BIG
@C
C4C3C2C1
Type = CIRCLEProp = BIG
@C1
Type = LINEProp = SMALL
@L
L4L3L2L1
Type = LINEProp = SMALL
@L1
Type = FIGURECD = TypeCD = Position
@C&L
C1 L1
Type = ?
@ ?
...
it
Type = FIGURECD = Type
@C&L
CIRCLE ¬CIR.
the circle
Discussion
Single mechanism for different kinds of reference– not linking, but extraction
bridging, one-anaphora, other-expressions integrated treatment of demonstratives (cf. full paper) takes into account visual information (required for dialogues)
Formalization of Cognitive Grammar– Implementation into a real dialogue platform– Partial validation on a corpus of human dialogues
other-expressions
– Being even for formal Expressing the constraints in the framework of S-DRT