  Multilingual programs, whose implementations are made of different languages,
are gaining traction especially in domains, such as web programming, that
particularly benefit from the additional flexibility brought by using multiple
languages. In this paper, we discuss the impact that the features commonly used
in multilingual programming have on our capability of specifying and analyzing
them. To this end, we first outline a few broad categories of multilingual
programming, according to the mechanisms that are used for inter-language
communication. Based on these categories, we describe several instances of
multilingual programs, as well as the intricacies that formally reasoning about
their behavior would entail. We also summarize the state of the art in
multilingual program analysis, including the challenges that remain open. These
contributions can help understand the lay of the land in multilingual program
specification and analysis, and motivate further work in this area.
