Reifying the Reflectogram: Towards Explicit Control for Implicit Reflection

Reflective facilities in OO languages are used both for implementing language extensions (such as AOP frameworks) and for supporting new programming tools and methodologies (such as object-centric debugging and message-based profiling). Yet controlling the run-time behavior of these reflective facilities introduces several challenges, such as computational overhead, the possibility of metarecursion and an unclean separation of concerns between base and meta-level. In this paper we present five dimensions of meta-level control from related literature that try to remedy these problems. These dimensions are namely: temporal and spatial control, placement control, level control and identity control. We argue that the reification of the descriptive notion of the reflectogram, can unify the control of meta-level execution in all these five dimensions. We present a model for the reification of the reflectogram and validate our approach through a prototype implementation in the Pharo programming environment. Finally we detail a case-study on run-time tracing illustrating our approach.