The basic abstraction mechanisms of Semantic Data Models -aggregation, classification and generalization -are considered the essential features to overcome the limitations of traditional data models in terms of semantic expressiveness. An important issue in database programming language design is which features should a programming language have to support the abstraction mechanisms of Semantic Data Models. This paper shows that when using a strongly typed programming language, that language

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... uld support the notion of type hierarchies to achieve a full integration of Semantic Data Models abstraction mechanisms within the language's type system. The solution is presented using the language Galileo, a strongly typed, interactive programming language specifically designed for database applications.