Object spaces for safe image surgery

Abstract

Long-lived systems rely on reflective self-modification to evolve. Unfortunately, since such a system is at both ends of a causal loop, this means modifications that impact the reflective layer itself can be overly difficult to apply. This paper introduces ObjectSpaces, a reification of the familiar Smalltalk image as a first-class entity. By confining the system inside an ObjectSpace, we isolate the evolution tools from it, while still giving them reflective access to the confined system. We describe the ObjectSpaces idea, the interface to communicate, inspect, and debug objects contained inside and ObjectSpace, based on a prototype implementation in GNU Smalltalk.