Nedetidsdefinisjoner

Nedetidsdefinisjoner refers to a class of definable mappings in model theory. Model theory is a subfield of mathematical logic that studies the relation between a formal language and the structures in which it is interpreted. The study of definability is central to model theory, with model theorists seeking to characterize the properties of a structure that make it possible to define certain subsets or relations in the structure.

Nedetidsdefinisjoner arises in the context of interpretations of formal languages. An interpretation assigns to each constant, function, and relation symbol in the language a corresponding entity in the structure - for instance, a constant could be interpreted as a specific element of the structure, while a relation symbol could be interpreted as a subset of pairs of elements in the structure. The living time of an interpretation, or its "nedetids" in Norwegian, constitutes the period over which it is considered valid.

A common challenge in model theory is determining whether or not a given subset or relation is defined by a formula of the language. Formulas typically take one of two forms: existential (which asserts the existence of an element satisfying a certain property), and universal (which asserts that every element in the structure satisfies a certain property). The relationship between the existence and validity of a formula in a structure often indicates the satisfaction of a given property.