A Formal Semantics for a Language with Type Extension

The purpose of this paper is to give a formal semantics for a language which includes type extension. Used in association with pointer variables, this forms the basis of object-orientation in the languages Oberon and Oberon-2 which have evolved from Modula-2. The focus is on the meaning of assignment because this is the important difference between such languages and the strongly-typed Pascal family. An abstract syntax is defined using the Z notation and the static and dynamic semantics are given in a denotational style