This monograph grew out of research at Xerox PARC and the Center for the Study of Language and Information (CSLI) during the first year of CSLI's existence. The Center was created as a meeting place for people from many different research traditions and there was much interest in seeing how the various approaches could be joined in a common effort to understand the complexity of language and information. CSLI was thus an ideal environment for our group and our enterprise. Our original goal was to see how a well-developed linguistic the ory, such as lexical-functional grammar, could be joined with the ideas emerging from research in situation semantics in a manner which would measure up to the technical standards set by Montague grammar. The outcome was our notion of situation schemata and the extension of constraint-based grammar formalisms to deal with semantic as well as syntactic information. As our work progressed we widened our approach. We decided to also include a detailed study of the logic of situation theory, and to investigate how this logical theory is related to the relational theory of meaning developed in situation semantics."

In recent years, 'semantical partiality' has emerged as an important concept in philosophical logic as well as in the study of natural language semantics. Despite the many applications, however, a number of mathematically intriguing questions associated with this concept have received only very limited attention. Partiality, Truth, and Persistence is a study in spatial model theory, the theory of partially defined models. First, with the introduction of truth value gaps in semantics, there are many ways to generalize the classical truth definition for the sentences of a first order predicate language. We know what it means for a sentence to be true or false in a classical, complete model, but how do we extend this relation when partial models are introduced? Various alternatives exist, and a detailed comparison is carried out between them. Since these studies concern a full first order predicate language, many distinctions appear that do not arise in the case of pure propositional logic. A condition of monotonicity or 'persistence' of truth relative to partial models has a prominent position among conditions that are not expressible in the framework of standard, complete model theory. The final chapter investigates the relation between such conditions and expressibility properties in general. These discussions culminate with a combined Lindstrom and persistence characterization theorem. Tore Langholm is a research fellow in mathematics at the University of Oslo. He is a co-author of Situations, Language and Logic.