The meaning of multilanguage programs

In this dissertation we develop a formal framework for examining multi-language systems. First, we introduce the framework with a simple language that connects two call-by-value languages with different type systems, and then we extend the language features we consider. This analysis allows us to reveal essential similarities in many different problems in programming language design, such as the surprising fact that safe foreign interfaces share a strong connection with contracts. We also explore the idea that a multi-language system ought to preserve the equational properties of its constituent languages and illustrate how to use this criterion as a design principle. Finally, we extend our methodology to domain-specific languages by presenting a formal design for Topsl, a domain-specific language for writing web-based surveys that is embedded into PLT Scheme.