Static Type Checking for the Kompics Component Model: Kola -- The Kompics Language

Abstract

Distributed systems are becoming an increasingly important part of systems and applications software and it is widely accepted that writing correct distributed systems is challenging. Message-passing concurrency models are the dominant programming paradigm and, even in statically typed languages, programming frameworks typically only have limited type checking support for messages, channels, and ports or mailboxes. In this paper, we present Kola, a language-level implementation of Kompics, a component model with message-passing concurrency. Kola comes with its own compiler and some special language constructs which extend Java's type system as necessary to enforce static type checking on messages, channels, and ports. We show that Kola improves the readability of Kompics code and removes opportunities to introduce bugs, at the cost of little compile time overhead and no runtime overhead.