Determinacy of Hierarchical Dataflow Model

A parallel computation model suitable for icon based visual programming languages is proposed. The model is uses to design a functional programming language for school children. A computation is specified by boxes and arrows forming a partially ordered set of nested boxes. Loops and Boolean data tokens are eliminated from the traditional dataflow model. Block structures are logical consistency (exception) are added. A declarative semantics of the model is defined formally. Using the formalism it is proved that the model is determinate