Distributed, Scalable, Dependable Real-Time Systems: Middleware Services and Applications

1 Computer Science & Engineering Dept.; University of Texas at Arlington; Box 19015, Arlington, TX 76019; {welch|shirazi}@cse.uta.edu The Bradley Dept. of Electrical and Computer Engineering;Virginia Polytechnic Institute and State University; Blacksburg, VA 24061;[email protected] 3 Code B35; Naval Surface Warfare Center,Dahlgren, VA 22448; {WermePV|MastersMW}@nswc.navy.mil Computer Sciences Corporation, Dahlgren, VA 22448 5 Ouachita Baptist University, 410 Ouachita Street, Arkadelphia, AR 71998-0001; [email protected] Abstract Some classes of real-time systems function in environments which cannot be modeled with static approaches. In such environments, the arrival rates of events which drive transient computations may be unknown. Also, the periodic computations may be required to process varying numbers of data elements per period, but the number of data elements to be processed in an arbitrary period cannot be known at the time of system engineering, nor can an upper bound be determined for the number of data items; thus, a worst case execution time cannot be obtained for such periodics. This paper presents middleware services that support such dynamic real-time systems through adaptive resource management. The middleware services have been implemented and employed for components of the experimental Navy system described in [WRHM96]. Experimental characterizations show that the services provide timely responses, that they have a low degree of intrusiveness on hardware resources, and that they are scalable.