together at last: how tense and aspect interact in simulation semantics nancy chang laura a....

ECG Theme Session ICLC03 University of La Rioja July 24, 2003ECG Theme Session ICLC03 University of La Rioja July 24, 2003

Together at Last:Together at Last:How Tense and Aspect How Tense and Aspect Interact in Simulation Interact in Simulation

SemanticsSemantics

Nancy ChangNancy Chang Laura A. Michaelis Laura A. Michaelis Srinivas NarayananSrinivas Narayanan

Department of Computer Department of Computer Science/International Science/International

Computer Science InstituteComputer Science Institute

UC BerkeleyUC Berkeley

[email protected]@icsi.berkeley.edu

Department of Linguistics/Department of Linguistics/

Institute of Cognitive ScienceInstitute of Cognitive Science

University of Colorado University of Colorado

at Boulderat Boulder

[email protected]@colorado.edu

Department of Computer Department of Computer Science/International Computer Science/International Computer

Science InstituteScience Institute

UC BerkeleyUC Berkeley

[email protected]@icsi.berkeley.edu


The ProblemThe Problem Aspectual theorists have proposed revealing models of Aspectual theorists have proposed revealing models of

type shifts, both explicit and implicit:type shifts, both explicit and implicit: Explicit type-shiftingExplicit type-shifting

• Progressive:Progressive: Process Process State (e.g., State (e.g., She was singingShe was singing))• Perfect:Perfect: Event Event State (e.g., State (e.g., The Eagle has landedThe Eagle has landed))

Implicit type-shifting (coercion)Implicit type-shifting (coercion)• State State episode of stasis episode of stasis:: She was depressed twiceShe was depressed twice..• State State inchoative event inchoative event: : I liked her within a minute.I liked her within a minute.

These models rely on an ontology of idealized situation These models rely on an ontology of idealized situation types (process, state, event, etc.).types (process, state, event, etc.).

In this respect, they are incompatible with models of In this respect, they are incompatible with models of tense.tense.


The ProblemThe Problem Unlike aspect, tense lacks an ontology.Unlike aspect, tense lacks an ontology. Tense is purely relational: there are no ‘tense-type Tense is purely relational: there are no ‘tense-type

entities’ corresponding to aspectual-type entities.entities’ corresponding to aspectual-type entities. Tense relates speech time to reference time (R).Tense relates speech time to reference time (R). R is located relative to the encoded situation; it R is located relative to the encoded situation; it

constrains inference potential.constrains inference potential. Tense semantics are therefore based on a location Tense semantics are therefore based on a location

metaphor: R is speaker/hearer location.metaphor: R is speaker/hearer location. By contrast, aspectual semantics are based on an entity By contrast, aspectual semantics are based on an entity

metaphor.metaphor. But tense and aspect are much more similar than the But tense and aspect are much more similar than the

traditional models imply.traditional models imply.


Tense-Aspect Interfaces Tense-Aspect Interfaces Tenses convey aspectual perspectives like ‘attention to Tenses convey aspectual perspectives like ‘attention to

endpoints’:endpoints’: My ex-husband is/was Latvian.My ex-husband is/was Latvian. I took a cab over. The driver was/?is Latvian.I took a cab over. The driver was/?is Latvian.

Aspect determines ‘direction of inclusion’ for R:Aspect determines ‘direction of inclusion’ for R: StateState: : Pat was in Cleveland Pat was in Cleveland in Junein June. . (state overflows R)(state overflows R) EventEvent: : Pat visited Cleveland Pat visited Cleveland in Junein June. . (event exhausted by R)(event exhausted by R)

Tense and aspect jointly encode overlap/sequence:Tense and aspect jointly encode overlap/sequence: I told them I I told them I had (had)had (had) more time on the meter. more time on the meter.

Tenses select aspectual types, and as such are coercion Tenses select aspectual types, and as such are coercion triggers. triggers. a eu a eu

Margot s’est retournée. Henri Margot s’est retournée. Henri avaitavait l’air heureux. l’air heureux. ‘‘Marge turned around. Harry was (perf/imperf) happy.’Marge turned around. Harry was (perf/imperf) happy.’


Our PurposeOur Purpose We will propose a simulation-based model of tense that We will propose a simulation-based model of tense that

is isomorphic to models of is isomorphic to models of phasal aspectphasal aspect proposed by proposed by Narayanan 1997 and Chang, Gildea & Narayanan 2000.Narayanan 1997 and Chang, Gildea & Narayanan 2000.

This model will capture tense-aspect interfaces, in This model will capture tense-aspect interfaces, in particular the role of tense in triggering aspectual type-particular the role of tense in triggering aspectual type-shifts.shifts.

We will use this model to account for two traditionally We will use this model to account for two traditionally mysterious kinds of semantic effects:mysterious kinds of semantic effects:

Habitual coercionHabitual coercion: : She took the bus to work that summer.She took the bus to work that summer. Present-tense coercionPresent-tense coercion: : She takes the bus to workShe takes the bus to work. .

We will model these type shifts by assuming x-schemas We will model these type shifts by assuming x-schemas for tense that are combinable with aspectual x-schemas.for tense that are combinable with aspectual x-schemas.

Tense x-schemas will be known as Tense x-schemas will be known as sampling setssampling sets..


Coercion by Tense: HabitualsCoercion by Tense: Habituals Habitual predications count as state predications:Habitual predications count as state predications:

ExtensibilityExtensibility• She smoked back then and I think she still does.She smoked back then and I think she still does.• *She enlisted in 1985 and I think she still does*She enlisted in 1985 and I think she still does..

Present-tense reportingPresent-tense reporting• She smokes.She smokes.• *Look! That woman smokes a cigar. *Look! That woman smokes a cigar.

However, via internal composition they are not states but However, via internal composition they are not states but iterated events (like pacing, bouncing a ball, etc.). iterated events (like pacing, bouncing a ball, etc.).

No predication is born habitual, so in the absence of a No predication is born habitual, so in the absence of a dedicated habitual marker, habitual meaning must come dedicated habitual marker, habitual meaning must come from an implicit type shift. from an implicit type shift.

But what grammatical form performs this type shift? But what grammatical form performs this type shift?


Coercion by Tense: Present Coercion by Tense: Present The present tense is a state selector (Langacker 1987):The present tense is a state selector (Langacker 1987):

**She is ill for three days.She is ill for three days. *She dribbles the basketball*She dribbles the basketball. .

Present distorts Aktionsart projected by predicators:Present distorts Aktionsart projected by predicators: Futures from perfective stem+present inflectionFutures from perfective stem+present inflection, e.g., Latin , e.g., Latin

amaboamabo ‘I will love’ (<amav + o) ‘I will love’ (<amav + o) Habitual-event reports:Habitual-event reports:

• She visits her motherShe visits her mother. (possible iff assigned a habitual reading). (possible iff assigned a habitual reading) ‘‘Progressive’ reports in, e.g., FrenchProgressive’ reports in, e.g., French: :

• Eh bien, à present, je me sens mieux. Le morale Eh bien, à present, je me sens mieux. Le morale revientrevient.. ‘Now I feel ‘Now I feel better. My morale is coming back.’ (Binet, better. My morale is coming back.’ (Binet, BidochonBidochon 8: 42) 8: 42)

‘‘Perfect’ reports in, e.g., French:Perfect’ reports in, e.g., French:• Ca fait dix minutes qu’elle nous Ca fait dix minutes qu’elle nous parleparle de la moquette! de la moquette! ‘She’s been ‘She’s been

telling us about the carpet for 10 minutes.’ (Binet, telling us about the carpet for 10 minutes.’ (Binet, BidochonBidochon 10:17) 10:17)


Simulation SemanticsSimulation Semantics

Inspired by biological control theory, Simulation Inspired by biological control theory, Simulation Semantics models events as executing-, or Semantics models events as executing-, or x-schemasx-schemas. .

An x-schema is a Petri net: a weighted graph consisting An x-schema is a Petri net: a weighted graph consisting of places (circles) and transitions (rectangles) connected of places (circles) and transitions (rectangles) connected by directed input and output arcs. by directed input and output arcs.

A state is defined by the placement of a token (a black A state is defined by the placement of a token (a black dot or number) in a particular place.dot or number) in a particular place.

The real-time execution The real-time execution semantics of Petri nets semantics of Petri nets models the production and consumption of resources:models the production and consumption of resources:

A transition is A transition is enabledenabled when its input places are marked such that it can when its input places are marked such that it can fire by movement of tokens from input to output.fire by movement of tokens from input to output.

Arcs include Arcs include resourceresource, , enableenable and and inhibitoryinhibitory arcs. arcs. Actions have Actions have hierarchical structurehierarchical structure, permitting embeddings., permitting embeddings.


Basic X-Schema DistinctionsBasic X-Schema Distinctions

StateState Obtains (Obtains (if markedif marked). ). Momentaneous Momentaneous

simulation/verificationsimulation/verification

TransitionTransition Fires to simulate an eventFires to simulate an event

Change of StateChange of State Transition entails pre- and Transition entails pre- and

post-states.post-states. Firing removes tokens from Firing removes tokens from

pre-state(s) and produces pre-state(s) and produces tokens on the post-state(s)tokens on the post-state(s)


X-Schemas and AktionsartX-Schemas and Aktionsart


A Schema ControllerA Schema Controller

• The controller sends signals to the embedded schema.• It transitions based on signals from the embedded schema.• It captures higher level coordination of actions.

Ready DoneStart Process Finish

SuspendCancel

interrupt resume

iterate


Phasal Aspects Map Phasal Aspects Map to Controllerto Controller


SuspendCancel

interrupt resume

IterateInceptive (start, begin) Iterative (repeat)

Completive (finish, end)Resumptive(resume)


Phases of Phases of ClimbClimb


SuspendCancel

interruptresume

Iterate

EnergyReady

StandingOn top

HoldFind hold

Pull(self)Stabilize

BINDINGS


About to ClimbAbout to Climb (Prospective) (Prospective)


SuspendCancel

interruptresume

Iterate

EnergyReady

StandingOn top

HoldFind hold

Pull(self)Stabilize

BINDINGS


Be- ClimbingBe- Climbing (Progressive) (Progressive)


SuspendCancel

interruptresume

Iterate

EnergyReady

StandingOn top

HoldFind hold

Pull(self)Stabilize

BINDINGS


Have- ClimbedHave- Climbed (Perfect) (Perfect)

EnergyReady

StandingOn top

HoldFind hold

Pull(self)Stabilize


SuspendCancel

interruptresume

Iterate

BINDINGS


Tense and Reference TimeTense and Reference Time

Tense is defined by the location of reference time Tense is defined by the location of reference time relative to speech time in the traditional (Reichenbach-relative to speech time in the traditional (Reichenbach-based) view:based) view:

Past tense = E,R < SPast tense = E,R < S Present tense = E,R,SPresent tense = E,R,S

In Simulation Semantics, R is a In Simulation Semantics, R is a statestate of the controller of the controller schema. schema.

The location of R relative to S is captured by a time-The location of R relative to S is captured by a time-depth representation called a depth representation called a sampling setsampling set: :

Present = single statePresent = single state Past = two states (onset and offset)Past = two states (onset and offset) The final or unique state is the state of knowledge at S.The final or unique state is the state of knowledge at S.


Aspect and Reference TimeAspect and Reference Time

In Simulation Semantics, ‘direction of inclusion’ In Simulation Semantics, ‘direction of inclusion’ is represented by the presence or absence of a is represented by the presence or absence of a transition between pre- and post-states in the transition between pre- and post-states in the sampling set.sampling set.

In the case of the present tense, there is only In the case of the present tense, there is only one state in the sampling set.one state in the sampling set.

Only states can be verified on the basis of a Only states can be verified on the basis of a single temporal sample.single temporal sample.

Therefore, present-tense reports are state Therefore, present-tense reports are state reports.reports.


Aspect and Reference TimeAspect and Reference Time

The sampling set for the past tense may include a The sampling set for the past tense may include a transition between the two states.transition between the two states.

The presence or absence of this transition captures the The presence or absence of this transition captures the difference between perfective and imperfective past:difference between perfective and imperfective past:

Perfective:Perfective: Pat was in Cleveland yesterday for the trade show Pat was in Cleveland yesterday for the trade show. . (yesterday includes offset transition)(yesterday includes offset transition)

Imperfective:Imperfective: Pat was in Cleveland yesterday, and in fact has Pat was in Cleveland yesterday, and in fact has been there all monthbeen there all month. (yesterday does not include an offset . (yesterday does not include an offset transition)transition)

The perfective and imperfective schemas are not The perfective and imperfective schemas are not alternate event types, nor are they alternate construals alternate event types, nor are they alternate construals of a single situation; they are sets of sets of places within of a single situation; they are sets of sets of places within the controller schema.the controller schema.


Aspectually Sensitive Aspectually Sensitive Past TensesPast Tenses Perfective

Imperfective


Type-Shifting RevisitedType-Shifting Revisited

In Simulation Semantics, a stative type shift is selection In Simulation Semantics, a stative type shift is selection of a state of the controller. of a state of the controller.

The combination of controller and base x-schema can The combination of controller and base x-schema can (a) augment, (b) embed or (c) select a part of the base x-(a) augment, (b) embed or (c) select a part of the base x-schema:schema:

AugmentationAugmentation: State : State inchoative state, e.g., inchoative state, e.g., Suddenly, I knew Suddenly, I knew the answerthe answer. .

EmbeddingEmbedding: Event : Event iterated event iterated event habitual state, e.g., habitual state, e.g., She She runsruns. .

SelectionSelection: Inchoative : Inchoative state, e.g., state, e.g., Your soup is cooled. Your soup is cooled. Additional examples: present-tense coercion, Additional examples: present-tense coercion,

progressive type-shifting, continuative perfect type-progressive type-shifting, continuative perfect type-shifting.shifting.


HabitualityHabituality

Habitual situations, e.g., Habitual situations, e.g., Jan ranJan ran, count as events, just , count as events, just like iterated actions, e.g., like iterated actions, e.g., Jan paced back and forthJan paced back and forth. .

Habituals are therefore not intrinsically stative; they are Habituals are therefore not intrinsically stative; they are events embedded in an events embedded in an iterateiterate schema: schema:

iterate


Stative CoercionStative Coercion

Habituals become stative solely by virtue of being Habituals become stative solely by virtue of being embedded in the stative process schema.embedded in the stative process schema.

This schema can be selected by the present tense.This schema can be selected by the present tense.

ongoingpresent


ConclusionConclusion In Simulation Semantics, tense and aspect are In Simulation Semantics, tense and aspect are

represented in a uniform manner. represented in a uniform manner. Rather than Aktionsart plus a time line and perspective, Rather than Aktionsart plus a time line and perspective,

we have combination of simulations. we have combination of simulations. Combinations model iteration, the selection of subparts Combinations model iteration, the selection of subparts

and augmentation of schemas.and augmentation of schemas. Using these mechanisms, we account for tense-based Using these mechanisms, we account for tense-based

coercions, e.g., stative coercion via present tense. coercions, e.g., stative coercion via present tense. How do we build ECG representations for tense How do we build ECG representations for tense

inflections that abstract over the various morphological inflections that abstract over the various morphological instantiations of tense (affixation, suppletion, etc.)?instantiations of tense (affixation, suppletion, etc.)?

Can we assume that English, like Romance, has both Can we assume that English, like Romance, has both state- and event-selecting past tenses? state- and event-selecting past tenses?

together at last: how tense and aspect interact in simulation semantics nancy chang laura a....

Documents

present tense

r tense

models of tense

presenttense coercion

tense semantics

event state

tensetype entities

role of tense