A Stack-Based Approach to Query Languages

Scoping, naming and binding are central concepts in the deenition and understanding of programming languages. With the introduction of sophisticated data models, these issues become important for query languages as well. Additionally, the goal of integrating query and programming languages requires a common basis for their operational semantics. We ooer here an approach to the deenition of the operational semantics of query languages based on an abstract machine, in which names, their bindings, and scopes deened by query and data structure are central. The machine has own simple data model for its store, and has a stack for dealing with scopes. We argue for the generality of the approach and illustrate it by deening the semantics of many query language primitives. Finally, we brieey consider how assignment and procedures can be neatly added.