LEAD + + : An Object - Oriented Re ective Language forDynamically Adaptable

A system has dynamic adaptability if it can adapt itself to dynamically changing runtime environments. As open-ended distributed systems and mobile computing systems have spread widely, the need for software with dynamic adaptability increases. We propose a model of software with dynamic adaptability and the object-oriented re-ective language LEAD++ based on the model. The basic idea is that we introduce the mechanism which changes procedure invocations dynamically depending on the states of runtime environments. The mechanism forms a meta-level architecture , and realizes dynamic adaptability in re-ective way. LEAD++ provides the mechanism as a language functionality. We are currently implementing a prototype of LEAD++ as a pre-processor of Java. Using LEAD++, we can systematically describe dynamically adaptable ap-plets, mobile objects, etc.