Explicitness in language design

The look and feel of a language is influenced by which of its concepts are made explicit. Explicit representations support language users in expressing their intent. They can help avoid hidden assumptions and provide manipulability of the exposed representation. On the other hand, explicit representations can lead to bigger and more complicated languages, cause extra burden for language users through notational overhead, and complicate the language design through a proliferation of feature interaction. In this talk I will give several examples of explicit representations and demonstrate their effect on language expressiveness and opportunities for analyses. I will then address how explicitness can serve as a language design criterion and what it takes to guide language designers in their decisions about making concepts explicit or not.