The Forest through the Trees

We have introduced several powerful techniques and formal tools: normalization rules that define a large language in terms of a smaller core; inference rules for defining both the dynamic evaluation of and static typing of expressions; and judgments for relating external values, internal values, and types.

The foundations of the techniques presented in this chapter are in logic and programming language theory. The main technique we use to specify XQuery's semantics is widely used, so much so that it goes by several names, including natural semantics, big-step semantics, and evaluation semantics; it is a special case of what is called operational semantics. The technique was originally proposed by Plotkin [STRUCTURAL ...

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