On Anchoring Sentences in Actions Action-Theoretic Approaches - PowerPoint PPT Presentation

On Anchoring Sentences in Actions Tillmann Pross Linguistic approaches On Anchoring Sentences in Actions Action-Theoretic Approaches Semantics and Philosophy in Europe 4 Temporal Anchors Summary Tillmann Pross Institute for Natural Language Processing University of Stuttgart 30.09.2011 1 / 29

On Anchoring Outline Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic 1 Linguistic approaches Approaches Temporal Anchors Summary 2 Action-Theoretic Approaches 3 Temporal Anchors 4 Summary 2 / 29

On Anchoring Linguistics vs. Action Theory Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches • Logical analysis of sentences that describe action vs. Temporal Anchors Logical analysis of action described by sentences Summary • Different focus and vocabulary of linguistic and action-theoretic approaches to the meaning of action sentences. • This talk: how can we combine linguistic and action-theoretic approaches to action sentences? 3 / 29

On Anchoring Sentences that describe action Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches • [Davidson, 1967]: The logical analysis of action sentences Temporal Anchors • Introduction of a new ontological sort of entities: “events” to Summary predicate logic – Brutus stabbed Caesar with a knife ⇒ Brutus stabbed Caesar. • Events link verbs with their arguments and adjuncts on a syntactic level. 4 / 29

On Anchoring Davidsonian Event Semantics Sentences in Actions Tillmann Pross • Semantic interpretation of Davidsonian Events? Linguistic • Interpret reference markers for events on par with approaches reference markers for “standard” individuals Action-Theoretic Approaches • Model contains a set of events with the help of which Temporal Anchors formulas containing event markers are evaluated Summary • E.g.: given a set of events E structured by < , a universe of individuals U and an interpretation function I , – [[ R ( e , x 1 ,..., x n )]] M , g = 1 iff � g ( e ) , g ( x 1 ) ,..., g ( x n ) � ∈ I ( R ) • where g is an assignment that maps e onto an element of E and x 1 ,..., x n onto elements of U . • Thus: events described by occurrences of e.g. “build a house” are events that stand in some ’build’- relation to the one who is doing the building (or the ones who are doing the building) and the thing that is built. 5 / 29

On Anchoring Fine grained event semantics? Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches Temporal Anchors • Davidsonian event semantics analyzes action sentences in Summary terms of relations between individuals and events, not in terms of the action that is described. • Causes problems when it comes to the subatomar structure of events (Moens and Steedman [1988]) 6 / 29

On Anchoring Example: Tense and Aspect Sentences in Actions Tillmann Pross Linguistic approaches • How to capture the different types of event complexes that Action-Theoretic can be described with action verbs? (“Aktionsart”, [Vendler, Approaches 1957]) Temporal Anchors – E.g. ’run’ vs. ’build a house’ vs. ’reach the top’ Summary • How to capture the interaction between aspect, tense and events? – E.g. John was building a house � John built a house But: John was running ⇒ John ran. • Complex subatomar structure of events that can not be captured with the specification of pre-/postconditions but is related to the actions that are described. 7 / 29

On Anchoring Action described by sentences Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic • Logical analysis of action described by sentences Approaches • Add modal operators to the language of propositional logic: Temporal Anchors Summary – STIT [Belnap et al., 2001] e.g.: “x sees to it that p” – BDI [Rao and Georgeff, 1991] e.g.: “x intends that p” • Semantic interpretation of these operators in a model theory with branching time • Connection between action-theoretic approaches and events? 8 / 29

On Anchoring Action-theoretic approach to events Sentences in Actions Tillmann Pross Linguistic • Experimental Evidence: Segmentation of events along the approaches assumption of underlying causal/plan-goal/intentional Action-Theoretic Approaches structures (see e.g. the collection of papers in [Shipley and Temporal Anchors Zacks, 2008]) Summary • Conceptual: Explanation of temporal variation with causal/ behavioral/intentional explanation patterns • Linguistics: Close connection between planning and events [van Lambalgen and Hamm, 2004] • Idea: use action logic to formalize the segmentation, constitution and internal structure of events. – But: Connection between natural language semantics and action formulas? 9 / 29

On Anchoring Anchors in Discourse Representation Theory Sentences in Actions Tillmann Pross (DRT) Linguistic approaches Action-Theoretic Approaches Temporal Anchors • Anchors were introduced to DRT [Kamp, 1984] as a means Summary to represent puzzles of reference in propositional attitude ascriptions ([Kamp, 1984-85, Asher, 1986]) • An anchor is a two-place relation between a discourse reference marker (a “floater”) and a specification of its relation of acquaintance (a “source”): � floater , source � 10 / 29

On Anchoring Linking Natural Language Semantics and Action Sentences in Actions Tillmann Pross Theory Linguistic approaches Action-Theoretic Approaches Temporal Anchors • Here: specify anchor sources for temporal entities with the Summary help of operators from action logic. • Consider not only pre-/postconditions of events but also the (sequence of) action (+ additional information on these actions such as intentions) which connect these conditions. • This talk: adopt ideas from the BDI-interpretation of CTL* proposed by [Singh, 1994] 11 / 29

On Anchoring Temporal anchors: Syntax and Semantics Sentences in Actions Tillmann Pross Linguistic approaches Syntactic representation of temporal anchors: Action-Theoretic Approaches e Temporal Anchors � e , x OP K � • Summary name ( e ) • where OP is one of the operators PATH,PLAN,INT and K a DRS. Semantic interpretation of temporal anchors: • OP specifies a (branching) temporal structure which is assigned to e by a function SEM n ame ( e ) . 12 / 29

On Anchoring Branching-time Structures Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches A branching-time structure is a tuple E = { T , I , Actions } , where Temporal Anchors • T = � <, Times � , where T is a labeled directed graph with Summary node set Times , arc set Actions and node labels given by I . In addition, we require the graph of T to be a tree. • I associates times t ∈ Times with interpretations, i.e. an information structure representing the state of affairs at t . 13 / 29

On Anchoring Branching-time Structures Sentences in Actions Tillmann Pross Linguistic approaches • Actions is a function from pairs � t , t ′ � of adjacent members Action-Theoretic of Times to Agents. Approaches Temporal Anchors • S ( x )( t ) is a function from Scenarios to agents at a time. A Summary scenario is any maximal set of moments containing the given moment, and all moments in its future along some particular branch. • P ( x )( t ) is a function from substructured of T . to agents at a time and assigns plans to agents. • Int ( x )( t ) is a function from T to agents at a time and assigns intentions to agents. 14 / 29

On Anchoring Example: Simple Past Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches Example (“Peter built a house”) Temporal Anchors e 0 , x , n Summary y � e 0 , x PATH � house ( y ) e 0 ≺ n build ( e 0 ) Peter ( x ) 15 / 29

On Anchoring Temporal anchors: Model-Theoretic Semantics (1) Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches Temporal Anchors • Past tense: e ≺ n Summary • � e , x PATH K � � M , S , t name ( e ) – iff ∃ [ S ; t , t 1 ] ∈ S ( x )( t ) sth. t 1 ≺ n and S ∈ SEM name ( e ) and � M , t 1 K 16 / 29

On Anchoring Example: Present Progressive Sentences in Actions Tillmann Pross Linguistic approaches Example (“Peter is building a house”) Action-Theoretic x , e 0 , n Approaches e 1 Temporal Anchors y Summary � e 1 , x PLAN � house ( y ) � e 0 , x INT � e 1 ⊆ e 0 e 0 < beg e 1 build ( e 1 ) n ∈ e 0 be ( e 0 ) Peter ( x ) 17 / 29

On Anchoring Temporal anchors: Model-Theoretic Semantics (2) Sentences in Actions Tillmann Pross Linguistic approaches Action-Theoretic Approaches • INT Temporal Anchors � e , x INT K � � M , t name ( e ) Summary – iff [ K ] M , t ∈ INT ( x )( t ) ; • PLAN: n ∈ e � e , x PLAN K � � M , S , P , t name ( e ) – iff ∃ [ S ; t 0 , n ] ∈ S ( x )( t ) and ∃ [ P ; n , { t 1 ,..., t n } ] ∈ P ( x )( t ) sth. ( S ∪ P ) ∈ SEM name ( e ) and ( � M , t 1 K ∧ ... ∧ � M , t n K ) 18 / 29

On Anchoring Example: Past Progressive Sentences in Actions Tillmann Pross Linguistic approaches Example (“Peter was building a house”) Action-Theoretic Approaches x , e 0 , n Temporal Anchors e 1 Summary y � e 1 , x PLAN � house ( y ) � e 0 , x INT � e 1 ⊆ e 0 build ( e 1 ) e 0 ≺ n be ( e 0 ) Peter ( x ) 19 / 29