Hearers and readers make inferences on the basis of what they hear or read. These inferences are partly determined by the linguistic form that the writer or speaker chooses to give to her utterance. The inferences can be about the state of the world that the speaker or writer wants the hearer or reader to conclude are pertinent, or they can be about the attitude of the speaker or writer vis-à-vis this state of affairs. The attention here goes to the inferences of the first type. Research in semantics and pragmatics has isolated a number of linguistic phenomena that make specific contributions to the process of inference. Broadly, entailments of asserted material, presuppositions (e.g., factive constructions), and invited inferences (especially scalar implicatures) can be distinguished.
While we make these inferences all the time, they have been studied piecemeal only in theoretical linguistics. When attempts are made to build natural language understanding systems, the need for a more systematic and wholesale approach to the problem is felt. Some of the approaches developed in Natural Language Processing are based on linguistic insights, whereas others use methods that do not require (full) semantic analysis.
In this article, I give an overview of the main linguistic issues and of a variety of computational approaches, especially those stimulated by the RTE challenges first proposed in 2004.
The term coordination refers to the juxtaposition of two or more conjuncts often linked by a conjunction such as and or or. The conjuncts (e.g., our friend and your teacher in Our friend and your teacher sent greetings) may be words or phrases of any type. They are a defining property of coordination, while the presence or absence of a conjunction depends on the specifics of the particular language. As a general phenomenon, coordination differs from subordination in that the conjuncts are typically symmetric in many ways: they often belong to like syntactic categories, and if nominal, each carries the same case. Additionally, if there is extraction, this must typically be out of all conjuncts in parallel, a phenomenon known as Across-the-Board extraction. Extraction of a single conjunct, or out of a single conjunct, is prohibited by the Coordinate Structure Constraint. Despite this overall symmetry, coordination does sometimes behave in an asymmetric fashion. Under certain circumstances, the conjuncts may be of unlike categories or extraction may occur out of one conjunct, but not another, thus yielding apparent violations of the Coordinate Structure Constraint. In addition, case and agreement show a wide range of complex and sometimes asymmetric behavior cross-linguistically. This tension between the symmetric and asymmetric properties of coordination is one of the reasons that coordination has remained an interesting analytical puzzle for many decades.
Within the general area of coordination, a number of specific sentence types have generated much interest. One is Gapping, in which two sentences are conjoined, but material (often the verb) is missing from the middle of the second conjunct, as in Mary ate beans and John _ potatoes. Another is Right Node Raising, in which shared material from the right edge of sentential conjuncts is placed in the right periphery of the entire sentence, as in The chefs prepared __ and the customers ate __ [a very elaborately constructed dessert]. Finally, some languages have a phenomenon known as comitative coordination, in which a verb has two arguments, one morphologically plural and the other comitative (e.g., with the preposition with), but the plural argument may be understood as singular. English does not have this phenomenon, but if it did, a sentence like We went to the movies with John could be understood as John and I went to the movies.
Željko Bošković and Troy Messick
Economy considerations have always played an important role in the generative theory of grammar. They are particularly prominent in the most recent instantiation of this approach, the Minimalist Program, which explores the possibility that Universal Grammar is an optimal way of satisfying requirements that are imposed on the language faculty by the external systems that interface with the language faculty which is also characterized by optimal, computationally efficient design. In this respect, the operations of the computational system that produce linguistic expressions must be optimal in that they must satisfy general considerations of simplicity and efficient design. Simply put, the guiding principles here are (a) do something only if you need to and (b) if you do need to, do it in the most economical/efficient way. These considerations ban superfluous steps in derivations and superfluous symbols in representations. Under economy guidelines, movement takes place only when there is a need for it (with both syntactic and semantic considerations playing a role here), and when it does take place, it takes place in the most economical way: it is as short as possible and carries as little material as possible. Furthermore, economy is evaluated locally, on the basis of immediately available structure. The locality of syntactic dependencies is also enforced by minimal search and by limiting the number of syntactic objects and the amount of structure accessible in the derivation. This is achieved by transferring parts of syntactic structure to the interfaces during the derivation, the transferred parts not being accessible for further syntactic operations.
Eve V. Clark
The words and word-parts children acquire at different stages offer insights into how the mental lexicon might be organized. Children first identify ‘words,’ recurring sequences of sounds, in the speech stream, attach some meaning to them, and, later, analyze such words further into parts, namely stems and affixes. These are the elements they store in memory in order to recognize them on subsequent occasions. They also serve as target models when children try to produce those words themselves. When they coin words, they make use of bare stems, combine certain stems with each other, and sometimes add affixes as well. The options they choose depend on how much they need to add to coin a new word, which familiar elements they can draw on, and how productive that option is in the language. Children’s uses of stems and affixes in coining new words also reveal that they must be relying on one representation in comprehension and a different representation in production. For comprehension, they need to store information about the acoustic properties of a word, taking into account different occasions, different speakers, and different dialects, not to mention second-language speakers. For production, they need to work out which articulatory plan to follow in order to reproduce the target word. And they take time to get their production of a word aligned with the representation they have stored for comprehension. In fact, there is a general asymmetry here, with comprehension being ahead of production for children, and also being far more extensive than production, for both children and adults. Finally, as children add more words to their repertoires, they organize and reorganize their vocabulary into semantic domains. In doing this, they make use of pragmatic directions from adults that help them link related words through a variety of semantic relations.
The central goal of the Lexical Semantic Framework (LSF) is to characterize the meaning of simple lexemes and affixes and to show how these meanings can be integrated in the creation of complex words. LSF offers a systematic treatment of issues that figure prominently in the study of word formation, such as the polysemy question, the multiple-affix question, the zero-derivation question, and the form and meaning mismatches question.
LSF has its source in a confluence of research approaches that follow a decompositional approach to meaning and, thus, defines simple lexemes and affixes by way of a systematic representation that is achieved via a constrained formal language that enforces consistency of annotation. Lexical-semantic representations in LSF consist of two parts: the Semantic/Grammatical Skeleton and the Semantic/Pragmatic Body (henceforth ‘skeleton’ and ‘body’ respectively). The skeleton is comprised of features that are of relevance to the syntax. These features act as functions and may take arguments. Functions and arguments of a skeleton are hierarchically arranged. The body encodes all those aspects of meaning that are perceptual, cultural, and encyclopedic.
Features in LSF are used in (a) a cross-categorial, (b) an equipollent, and (c) a privative way. This means that they are used to account for the distinction between the major ontological categories, may have a binary (i.e., positive or negative) value, and may or may not form part of the skeleton of a given lexeme. In order to account for the fact that several distinct parts integrate into a single referential unit that projects its arguments to the syntax, LSF makes use of the Principle of Co-indexation. Co-indexation is a device needed in order to tie together the arguments that come with different parts of a complex word to yield only those arguments that are syntactically active.
LSF has an important impact on the study of the morphology-lexical semantics interface and provides a unitary theory of meaning in word formation.
Derivational morphology is a type of word formation that creates new lexemes, either by changing syntactic category or by adding substantial new meaning (or both) to a free or bound base. Derivation may be contrasted with inflection on the one hand or with compounding on the other. The distinctions between derivation and inflection and between derivation and compounding, however, are not always clear-cut. New words may be derived by a variety of formal means including affixation, reduplication, internal modification of various sorts, subtraction, and conversion. Affixation is best attested cross-linguistically, especially prefixation and suffixation. Reduplication is also widely found, with various internal changes like ablaut and root and pattern derivation less common. Derived words may fit into a number of semantic categories. For nouns, event and result, personal and participant, collective and abstract noun are frequent. For verbs, causative and applicative categories are well-attested, as are relational and qualitative derivations for adjectives. Languages frequently also have ways of deriving negatives, relational words, and evaluatives. Most languages have derivation of some sort, although there are languages that rely more heavily on compounding than on derivation to build their lexical stock. A number of topics have dominated the theoretical literature on derivation, including productivity (the extent to which new words can be created with a given affix or morphological process), the principles that determine the ordering of affixes, and the place of derivational morphology with respect to other components of the grammar. The study of derivation has also been important in a number of psycholinguistic debates concerning the perception and production of language.
Evaluative morphology is a field of linguistic studies that deals with the formation of diminutives, augmentatives, pejoratives, and amelioratives. Actually, evaluative constructions cross the boundaries of morphology, and are sometimes realized by formal strategies that cannot be numbered among word formation processes. Nevertheless, morphology plays a dominant role in the formation of evaluatives. The first attempt to draw an exhaustive account of this set of complex forms is found in the 1984 work Generative Morphology, by Sergio Scalise, who made the hypothesis that evaluatives represent a separate block of rules between inflection and derivation. This hypothesis is based on the fact that evaluatives show some properties that are derivational, others that are inflectional, and some specific properties that are neither derivational nor inflectional. After Scalise’s proposal, almost all scholars have tried to answer the question concerning the place of evaluative rules within the morphological component. What data reveal is that, in a cross-linguistic perspective, evaluatives display a uniform behavior from a semantic and functional point of view, but exhibit a wide range of formal properties. In other words, functional identity does not imply formal identity; consequently, we can expect that constructions performing the same function display different formal properties in different languages. So, if evaluatives are undoubtedly derivational in most Indo-European languages (even if they cannot be considered a typical example of derivation), they are certainly quite close to inflection in some Bantu languages. This means that the question about the place of evaluatives within the morphological component probably is not as crucial as scholars have thought, and that other issues, sometimes neglected in the literature, deserve the same attention. Among them, the role of pragmatics in the description of evaluatives is no doubt central. According to Dressler and Merlini Barbaresi, in their 1994 work, Morphopragmatics: Diminutives and Intensifiers in Italian, German and Other Languages, evaluative constructions are the more typical instantiation of morphopragmatics, which is “defined as the area of general pragmatic meanings of morphological rules, that is of the regular pragmatic effects produced when moving from the input to the output of a morphological rule.” Evaluatives include “a pragmatic variable which cannot be suppressed in the description of [their] meaning.” Another central issue in studies on evaluative morphology is the wide set of semantic nuances that usually accompany diminutives, augmentatives, pejoratives, and amelioratives. For example, a diminutive form can occasionally assume a value that is attenuative, singulative, partitive, appreciative, affectionate, etc. This cluster of semantic values has often increased the idea that evaluatives are irregular in nature and that they irremediably avoid any generalization. Dan Jurafsky showed, in 1996, that these different meanings are often the outcome of regular and cross-linguistically recurrent semantic processes, both in a synchronic and in a diachronic perspective.
Japanese is a language where the grammatical status of arguments and adjuncts is marked exclusively by postnominal case markers, and various argument realization patterns can be assessed by their case marking. Since Japanese is categorized as a language of the nominative-accusative type typologically, the unmarked case-marking frame obtained for transitive predicates of the non-stative (or eventive) type is ‘nominative-accusative’. Nevertheless, transitive predicates falling into the stative class often have other case-marking alignments, such as ‘nominative-nominative’ and ‘dative-nominative’. Consequently, Japanese provides much more varying argument realization patterns than those expected from its typological character as a nominative-accusative language.
In point of fact, argument marking can actually be much more elastic and variable, the variations being motivated by several linguistic factors. Arguments often have the option of receiving either syntactic or semantic case, with no difference in the logical or cognitive meaning (as in plural agent and source agent alternations) or depending on the meanings their predicate carry (as in locative alternation). The type of case marking that is not normally available in main clauses can sometimes be obtained in embedded contexts (i.e., in exceptional case marking and small-clause constructions). In complex predicates, including causative and indirect passive predicates, arguments are case-marked differently from their base clauses by virtue of suffixation, and their case patterns follow the mono-clausal case array, despite the fact that they have multi-clausal structures.
Various case marking options are also made available for arguments by grammatical operations. Some processes instantiate a change on the grammatical relations and case marking of arguments with no affixation or embedding. Japanese has the grammatical process of subjectivization, creating extra (non-thematic) major subjects, many of which are identified as instances of ‘possessor raising’ (or argument ascension). There is another type of grammatical process, which reduces the number of arguments by virtue of incorporating a noun into the predicate, as found in the light verb constructions with suru ‘do’ and the complex adjective constructions formed on the negative adjective nai ‘non-existent.’
Lexical semantics is the study of word meaning. Descriptively speaking, the main topics studied within lexical semantics involve either the internal semantic structure of words, or the semantic relations that occur within the vocabulary. Within the first set, major phenomena include polysemy (in contrast with vagueness), metonymy, metaphor, and prototypicality. Within the second set, dominant topics include lexical fields, lexical relations, conceptual metaphor and metonymy, and frames. Theoretically speaking, the main theoretical approaches that have succeeded each other in the history of lexical semantics are prestructuralist historical semantics, structuralist semantics, and cognitive semantics. These theoretical frameworks differ as to whether they take a system-oriented rather than a usage-oriented approach to word-meaning research but, at the same time, in the historical development of the discipline, they have each contributed significantly to the descriptive and conceptual apparatus of lexical semantics.
Natural language ontology is a branch of both metaphysics and linguistic semantics. Its aim is to uncover the ontological categories, notions, and structures that are implicit in the use of natural language, that is, the ontology that a speaker accepts when using a language. Natural language ontology is part of “descriptive metaphysics,” to use Strawson’s term, or “naive metaphysics,” to use Fine’s term, that is, the metaphysics of appearances as opposed to foundational metaphysics, whose interest is in what there really is.
What sorts of entities natural language involves is closely linked to compositional semantics, namely what the contribution of occurrences of expressions in a sentence is taken to be. Most importantly, entities play a role as semantic values of referential terms, but also as implicit arguments of predicates and as parameters of evaluation.
Natural language appears to involve a particularly rich ontology of abstract, minor, derivative, and merely intentional objects, an ontology many philosophers are not willing to accept. At the same time, a serious investigation of the linguistic facts often reveals that natural language does not in fact involve the sort of ontology that philosophers had assumed it does.
Natural language ontology is concerned not only with the categories of entities that natural language commits itself to, but also with various metaphysical notions, for example the relation of part-whole, causation, material constitution, notions of existence, plurality and unity, and the mass-count distinction.
An important question regarding natural language ontology is what linguistic data it should take into account. Looking at the sorts of data that researchers who practice natural language ontology have in fact taken into account makes clear that it is only presuppositions, not assertions, that reflect the ontology implicit in natural language.
The ontology of language may be distinctive in that it may in part be driven specifically by language or the use of it in a discourse. Examples are pleonastic entities, discourse referents conceived of as entities of a sort, and an information-based notion of part structure involved in the semantics of plurals and mass nouns. Finally, there is the question of the universality of the ontology of natural language. Certainly, the same sort of reasoning should apply to consider it universal, in a suitable sense, as has been applied for the case of (generative) syntax.