A Domain-specific Type System for Component Assemblages

Building complex software architectures can be subject to subtle assemblage errors that are typically not captured by classical type systems available with host programming languages such as Java, C#, or ML. Our real-life motivating example is the Dream component-based framework, that has been developed to facilitate the construction of configurable communication subsystems. To avoid assemblage errors in the Dream framework, we introduce a new type system, together with its type checking and type inference algorithms. Our type system can actually be used with any model where components interact by exchanging structured messages on ports. Types in our system build approximations of component behaviors, and allow verifying that message handling operations remain consistent within a whole configuration. Technically, our type system combines extensible record types with row variables, together with set and process types. Inference is aided by the use of sparse type annotations, and operates by propagating type information in a configuration graph.