The design and application of structured types in Ptolemy II

Ptolemy II is a component-based design and modeling environment. It has a polymorphic type system that supports both the base types and structured types, such as arrays and records. This paper presents the extensions to the base type system that support structured types. In the base type system, all the types are organized into a type lattice, and type constraints in the form of inequalities can be solved efficiently over the lattice. We take a hierarchical and granular approach to add structured types to the lattice, and extend the format of inequality constraints to allow arbitrary nesting of structured types. We also analyze the convergence of the constraint solving algorithm on an infinite lattice after structured types are added. To show the application of structured types, we present a Ptolemy II model that implements part of the IEEE 802.11 specifications. This model makes extensive use of record types to represent the protocol messages in the system.