In the real world, however, programmers use a mainstream programming language someone else picked for them. To address this conflict, they resort to—and on occasion build their own—domain-specific languages embedded in the chosen language (embedded domain-specific languages, or eDSLs). For example, JavaScript programmers employ jQuery for interacting with the Document Object Model and React for dealing with events and concurrency. As developers solve their problems in appropriate eDSLs, they compose these solutions into one system; that is, they effectively write multilingual software in a common host language.

Sadly, multilingual eDSL programming is done today on an ad hoc basis and is rather cumbersome. To create and deploy a language, programmers usually must step outside the chosen language to set up configuration files and run compilation tools and link-in the resulting object-code files. Worse, the host languages fail to support the proper and sound integration of components in different eDSLs. Moreover, most available integrated development environments (IDEs) do not even understand eDSLs or perceive the presence of code written in eDSLs.