DenoteS leftSubTree progressionS Denotational progressionfactorial 表示的意味論 Denotefactorial rightSubTree eval Clinger lookup アクター pushout denotacional progressionSi 操作的意味論 getLeft Korff PCF Communicating factorial descendantsf Bakker Processes getRight Semantics デイナ・スコット progressionf Baeten Abramsky Concurrency nondeterminism Computation Hoare Doctoral 遅延評価 Dissertation editors Domains 不動点 graph Concurrent Hewitt Customer parallelism immediate Methodology ECS vee Algebraic