REFLECTIONS ON AN ADAPTABLE REAL-TIME METALEVEL ARCHITECTURE

Existing reflective object-oriented real-time systems typically provid e the programmer with a single mechanism or policy. With the advent of a new generation of application software with demand for (soft) real- time behavior, this limited choice may not be sufficient. We propose a metalevel architecture, where an application can choose from differen t real-time mechanisms and policies, thereby configuring its real-time behavior dynamically at run-time. This allows the adaptation to requi rements that are not anticipated during application development. An ex ample from the field of multimedia systems motivates our approach. We achieve this adaptability by structuring our metalevel into separate e ntities concerned with the support of different areas such as active o bject models, scheduling, and synchronization. These entities implemen t a variety of different real-time mechanisms and policies. This metal evel architecture is implemented using standard reflective mechanisms such as metalevel interceptions and metaobject protocols. Some prelimi nary performance figures give an impression of the price that has to b e paid when our approach is used. (C) 1996 Academic Press, Inc.