Situation semantics is a framework informal semantics andsituation theory in which the meanings of linguistic expressions are evaluated with respect tosituations—partial, concrete parts or aspects of the world—rather than completepossible worlds. It was developed in the late 1970s and early 1980s byJon Barwise andJohn Perry as an alternative to extensional model theory and possible-worlds semantics, with a particular focus onperception reports, attitude reports and other context-dependent constructions in natural language.[1][2]
Situation semantics is underpinned bysituation theory, a general mathematical theory of information developed by Barwise, Perry, Keith Devlin and others, which introduces formal objects such asinfons (units of information), constraints and types to model how information is carried and flows between situations.[3][4]
In contemporary formal semantics, situation-based approaches include both the original Barwise–Perry programme and a more widely adopted family of theories (associated especially withAngelika Kratzer) that treat situations as parts of possible worlds and use situation variables in otherwise orthodox possible-worlds semantics.[5]
Situations entered formal semantics through Barwise's paper "Scenes and Other Situations" (1981), which analysednaked infinitive perception reports such asBeryl saw Meryl feed the animals in terms of an actually perceived situation that supports the embedded clause, rather than in terms of propositions alone.[6][5] Related papers by Barwise and Perry developed a broadly similar approach to belief reports and other problematic constructions.[7]
The bookSituations and Attitudes (1983) provided the first systematic statement of situation semantics. It proposed that linguistic meaning should be understood in terms of relations between three kinds of situations: adiscourse situation (in which an utterance is produced), aresource orconnective situation (representing background information, constraints and shared context), and adescribed situation (the situation talked about).[1] The framework was designed to capture how speakers use information available in limited parts of the world to talk about other parts, and to account for so-called "semantic universals" such as the external, information-conveying role of language.[2]
Early formulations of situation semantics faced foundational problems when cast in standard well-founded set theory, especially when modelling information flow and self-referential structures.[8] Building onPeter Aczel's work in non-well-founded set theory, Barwise and colleagues developedsituation theory as a general theory of information with a rich ontology of situations, infons, types and constraints, and used it to reformulate the semantic programme.[8][4]
Keith Devlin's work in the late 1980s and early 1990s further systematised situation theory, introducing infons as formal items of information and emphasising the distinction between information, its content and its various representations.[3][9] Situation theory subsequently developed into a general interdisciplinary framework for modelling information in logic, linguistics, philosophy of information and computer science.[4]
Barwise and Perry's original proposals for perception reports were challenged by, among others, James Higginbotham, who argued for an extensional alternative based onDavidsonian event semantics.[10][5] More generally, critics observed that many of the empirical motivations for situations could be addressed in frameworks that kept standard possible-worlds machinery while enriching it with events or additional parameters.
Although the specific Barwise–Perry framework lost much of its momentum in the early 1990s, a situation-based perspective remained influential. Kratzer and others developed a strand of situation semantics that treats situations as parts of possible worlds and uses them to model topic situations, domain restrictions and fine-grained content.[11][5] According to Barbara Partee, such "possible-worlds-based" situation semantics has had more impact on mainstream formal semantics than the original information-theoretic programme of Barwise and Perry.[12]
In situation semantics,situations are limited, concrete parts or aspects of the world that an agent can in principle perceive, keep track of and reason about. They are often described as "small worlds" containing individuals standing in relations and having properties at particular times and locations.[13] Situations can include, for example, a particular episode of feeding animals, a traffic intersection at a given time, or a specific conversational exchange.
Unlike complete possible worlds, situations are incomplete: for many propositionsp, neitherp nor ¬p need be settled by a given situation. This partiality is central to the programme: language users typically have access only to limited parts of reality, yet they use information available in those parts to draw conclusions about other parts.[1][5]
Later formulations of situation theory and situation semantics introduceinfons as abstract items of information. Intuitively, an infon corresponds to a simple state of affairs, such as an object having a property or a tuple of objects standing in a relation. A common notation represents infons as tuples of the form ⟨R,a₁, …,aₙ,p⟩, whereR is ann-place relation, theaᵢ are objects, andp is a polarity indicating whether the information is positive or negative.[3][14][15]
Given a suitable ontology of situations and infons, situation theory distinguishes several key relations:
On this view, information flow is governed by constraints—some nomic (laws of nature), some conventional (linguistic or social conventions), some logical or mathematical. These constraints explain how limited local information can yield knowledge about more remote or abstract aspects of the world.[4][3]
In the original Barwise–Perry framework, the meaning of an utterance is analysed as a relation between:
For example, a direct perception report such asBeryl saw Meryl feed the animals is analysed as asserting the existence of a past situations which Beryl saw and which supports the infon corresponding toMeryl feed the animals. The verbsee is thus treated as taking a situation rather than a proposition as its primary semantic argument.[6][5]
More generally, sentences impose conditions on situations, and complex expressions (such as definite descriptions, quantifier phrases or pronouns) may introduce or depend on situation variables. This allows the framework to model phenomena such as incomplete descriptions, shifting quantifier domains and context-sensitive anaphora.
Situation semantics was explicitly conceived as an alternative to possible-worlds semantics.[2][5] Both frameworks evaluate expressions relative to parameters beyond the actual world, but they differ in how those parameters are understood and used:
Even within possible-worlds semantics, however, it has become common to augment the evaluation point with additional coordinates, including times, locations and situations. Kratzer's work develops an approach in which situations are regarded as parts of worlds, with semantic composition often involving both a world and a "topic situation" parameter.[5][11] From this perspective, situation semantics and possible-worlds semantics are less competing theories than different ways of organising the same ingredients.
The Barwise–Perry programme emphasised:
This version of situation semantics was applied to direct perception reports, de re belief reports, pronouns and demonstratives, and various kinds of context-dependent expressions.[1][9] Much of this work is collected in the multi-volume seriesSituation Theory and Its Applications.[16]
As developed by Devlin, Seligman, Moss and others, situation theory abstracts away from specifically linguistic phenomena and offers a general account of information content, types, parameters and constraints. It provides basic types for individuals, locations, times, relations, situations, infons and other constructs, and uses type abstraction and constraint satisfaction to model information flow.[4][3][17]
This abstract framework has been applied outside linguistics, including in knowledge representation, information retrieval and context-aware computing.[18]
A distinct line of work, associated particularly with Angelika Kratzer, builds situation-based semantics on top of possible-worlds semantics. On this approach:
This framework has been used to develop detailed analyses of, among other topics, implicit quantifier domain restrictions, so-calleddonkey pronouns, exhaustive interpretations, and the integration of situation semantics with Davidsonian event semantics.[5] It has also inspired extensive work on situation variables in determiner phrases and other constituents.[19][20]
More recent work connects situation semantics totruthmaker semantics and alternative-based approaches. Some authors treat situations (or closely related entities such as "cases") as truthmakers or as elements in alternative sets used to capture focus and inquisitive content.[21] In such frameworks, ideas from situation semantics contribute to debates about the ontology of facts, the structure of propositions and the semantics of modality and conditionals.
Situation semantics played a central role in early work onhead-driven phrase structure grammar (HPSG). Pollard and Sag adopted a situation-based semantics for HPSG in order to integrate syntactic, semantic and pragmatic information in a single constraint-based formalism.[22] Later HPSG work on interrogatives and dialogue, such as Ginzburg and Sag'sInterrogative Investigations, also draws on situation-semantic ideas.[23]
A survey of HPSG notes that the framework "started out with situation semantics (Barwise & Perry 1983)" before later adoptingMinimal Recursion Semantics as a more underspecified semantic interface.[24]
Beyond HPSG, situation semantics and situation variables are widely used in contemporary work on:
In philosophical logic and the philosophy of language, situation semantics has influenced debates about the nature of propositions, facts and information. Some authors treat situations or infons as candidates for fine-grained contents that can play the role of truthmakers, mental contents or objects of attitudes, in contrast to more coarse-grained sets of worlds.[11][26]
Situation theory, in turn, has contributed to a family of logics and models for information flow, sometimes in combination with ideas fromFred Dretske's theory of information.[27]
Situation-theoretic notions have been applied in computational linguistics, knowledge representation and context-aware systems. Examples include information-retrieval models based on situation theory and work on situation-aware services where detectable situations are manipulated as objects in formal systems.[28][29]