Language Symbiosis through Symbiotic Reflection

Meta-programming is the act of using one system or language to reason about another one. Reflection describes systems that have access to and change a causally connected representation of themselves, hence leading to self-extensible systems. In reflective languages, only one language is used, while in meta-programming two languages play a role (the base language and the meta language). In this paper we introduce symbiotic reflection, a form of reflection between two languages where both languages play the base and the meta-language role. New in this approach is that symbiotic reflection integrates languages from different paradigms in such a way that they both represent, reason about and act upon each other. We illustrate symbiotic reflection with SOUL, a logic programming language in symbiotic reflection with the object-oriented programming language Smalltalk. We show how SOUL does logic reasoning directly on Smalltalk objects, and how to use this to implement type snooping and second order logic programming.