Weak Protection for Reflective Operating Systems

A customizable scheduler for real-time computing is a typical example of the advantage of an extensible operating system. We have applied reflection to a traditional operating system and experimentally implemented a customizable scheduler for real-time computing. This paper reports this experience and discusses the limitation we encountered. Then this paper proposes that a mechanism we call weak protection is needed to make a reflective operating system workable. 1 A Design of Reflective Systems Although there are various definitions of reflective systems, a typical reflective system can be expressed as a system that exposes part of modules in the system and makes it possible for the users to replace the modules. The interface to the exposed module is designed in an object-oriented method, and hence the modules are often called metaobjects. Also, the exposed modules should satisfy the following criteria: ffl Scope control: The user can control the scope where the substituted module i...