LEAD++: An object-oriented reflective language for dynamically adaptable software model

A software system has dynamic adaptability if it can adapt itself to dynami cally changing runtime environments. As open-ended distributed systems and mobile computing systems have spread widely, the need for software systems with dynamic adaptability increases. We propose a software model with dynam ic adaptability called DAS and its description language LEAD++. The basic m echanism for dynamic adaptability is called adaptable procedure. An adaptab le procedure is a special kind of generic procedures (functions) whose meth ods are selected based upon the state of its runtime environment. Furthermo re, control mechanisms of adaptable procedures - including method selection strategies - are realized using generic procedures. This sort of reflectiv e architecture enables us to write a dynamically adaptable software system in highly flexible, extensible, readable and maintainable way. LEAD++ is an object-oriented reflective language that provides adaptable procedures and their control mechanisms as its basic language functionalities. We are cur rently implementing a prototype of LEAD++ as a pre-processor of Java. Using LEAD++, we can systematically describe dynamically adaptable applets, mobi le objects, etc.