in Stack-Based Query Languages

In this report we propose a new approach to types and static type checking in object-oriented database query and programming languages. In contrast to typical approaches to types which involve very advanced mathematical concepts we present a type system from the practitioners ’ point of view. We argue that many features of current object-oriented query/programming languages, such as ellipses, automatic coercions and irregularities in data structures, cause that very formal type systems are irrelevant to practical situations. We treat types as some syntactic qualifiers (tokens or some structures of tokens) attached to objects, procedures, modules and other data/program entities. Such syntactic qualifiers we call signatures. We avoid the simpleminded notion that a type has some internal semantics e.g. as a set of values. In our assumptions a type inference system is based on predefined decision tables involving signatures and producing type checking decisions, which can be the following: (1) type error, (2) new signature, (3) dereference