Semiotics, the general theory of sign-processes and languages, considers three aspects under which these processes may be studied, viz. a syntactic one, a semantic one, and a pragmatic one. The aim of this course is to introduce and discuss foundational issues concerning these aspects within the framework of what could, generally, be called the formal and computational study of natural language as it developed during the second half of this century. Students should be able to evaluate critically recent formal theories of language.
Familiarity with propositional and predicate logic.
Is also included in other courses
In a first part which concentrates on syntax - in which languages are categorized according to their complexity, or, more exactly, according to the complexity of the rule systems or grammars needed to characterize them - the Chomsky-Hierarchy of Grammars will be introduced in view of the discussion whether natural languages are 'context-free' or 'context-sensitive' with special reference to issues of Turing-computability and applicability to natural-language Parsing. Among the grammars discussed here are the Categorial Grammars based on the work of the logician Ajdukiewicz. They will provide the link with the second part which considers recent developments in the study of natural language semantics that grew out of the interest in the foundations of mathematics and the (model-theorectic) semantics of formal logic. Central to this approach are the concepts of 'Truth', 'Denotation', Compositionality' and the 'Intension-Extension'-distinction. In this part we will concentrate on the 'Possible-Worlds'- or 'Model-theoretic'-Semantics developed by R. Montague, discuss its logical-philosophical background (intensional contexts, opacity, lambda-abstraction, the semantics of propositionnal attitudes) and show its feasibility in the field of machine-translation and computer
programming. Continuing this development and extending its field to the general structure of semantic objects and their formal properties is the theory of Generalized Quantifiers. Subsequently, an alternative to this approach, Situation Semantics which rejects both the (fregean) principle of the compositionality of interpretation and the centrality of truth-values as the references of propositions, will be discussed and both approaches will be compared. A final part introduces developments in formal pragmatics - the study of utterance-meaning' i.e. the meanings of sentences in a specific context - in relation to formal semantics. More specifically, Discourse Representation Theory will be focused upon here. Its aim is twofold. On the one hand, presenting a possible synthesis of two views of meaning, viz. the Truth-conditional or model theoretic one and the Procedural view. On the other hand, extending the domain of formal semantics from sentences to 'texts' (or 'Discours') thus (partly) unifying the field of natural language processing.