Definition and Examples of Semantic Entailment

In semantics  and pragmatics, entailment is the principle that under certain conditions the truth of one statement ensures the truth of a second statement. Also called strict implication,  logical consequence, and semantic consequence. The two types of entailment that are the most frequent in language, says  Daniel Vanderveken, are truth conditional and illocutionary entailments. For example, he says, the performative sentence I beg you to help me illocutionary entails the imperative sentence Please, help me! and truth conditionally entails the declarative sentence You can help me (Meaning and Speech Acts: Principles of Language Use, 1990). Commentary [O]ne statement entails another when the second is a logically necessary consequence of the first, as Alan lives in Toronto entails Alan lives in Canada. Note that the relationship of entailment, unlike that of paraphrase, is one-way: it is not the case that Alan lives in Canada entails Alan lives in Toronto. (Laurel J. Brinton, The Structure of Modern English: A Linguistic Introduction. John Benjamins, 2000) [M]any, if not all, assertive sentences (statements, propositions) of a language allow for inferences solely on the basis of their meanings. For example, when I say Ben has been murdered, then anyone who has understood this utterance and accepts its truth will also accept the truth of the statement Ben is dead. (Pieter A. M. Seuren, Western Linguistics: An Historical Introduction. Wiley-Blackwell, 1998) Entailment Relations An entailment can be thought of as a relationship between one sentence or set of sentences, the entailing expressions, and another sentence, what is entailed... We can find countless examples where entailment relations hold between sentences and countless where they do not. The English sentence (14) is normally interpreted so that it entails the sentences in (15) but does not entail those in (16). (14) Lee kissed Kim passionately. (15)a. Lee kissed Kim.b. Kim was kissed by Lee.c. Kim was kissed.d. Lee touched Kim with her lips. (16)a. Lee married Kim.b. Kim kissed Lee.c. Lee kissed Kim many times.d. Lee did not kiss Kim. (Gennaro Chierchia and Sally McConnell-Ginet, Meaning and Grammar: An Introduction to Semantics. MIT Press, 2000) The Challenge of Determining Meaning Semantic entailment is  the task of determining, for example, that the sentence: Wal-Mart defended itself in court today against claims that its female employees were kept out of jobs in management because they are women entails that Wal-Mart was sued for sexual discrimination. Determining whether the meaning of a given text snippet entails that of another or whether they have the same meaning is a fundamental problem in natural language understanding that requires the ability to extract over the inherent syntactic and semantic variability in natural language. This challenge is at the heart of many high-level natural language processing tasks including Question Answering, Information Retrieval and Extraction, Machine Translation, and others that attempt to reason about and capture the meaning of linguistic expressions.Research in natural language processing in the last few years has concentrated on developing resources that provide multiple levels of syntactic and semantic analysis, resolve context sensitive ambiguities, and identify relational structures and abstractions.... (Rodrigo de Salvo Braz et al., An Inference Model for Semantic Entailment in Natural Languages.  Machine Learning Challenges: Evaluating Predictive Uncertainty, Visual Object Classif ication and Recognizing Textual Entailment, ed. by  Joaquin Quià ±onero  Candela et al. Springer, 2006)