We present a utility accrual real-time scheduling algorithm called CIC-VCUA, for tasks whose execution times are functions of their starting times. We model such variable execution times employing variable cost functions (or VCFs). The algorithm considers application activities that are subject to time/utility function time constraints (or TUFs), execution times described using VCFs, and concurrent, mutually exclusive sharing of non-CPU resources. We consider the multi-criteria scheduling objective of (1) assuring that the maximum interval between any two consecutive, successful completions of jobs of a task must not exceed a specified upper bound, and (2) maximizing the system's total accrued utility, while satisfying mutual exclusion resource constraints. Since the scheduling problem is intractable, CIC-VCUA statically computes worst-case sojourn times of tasks, selects tasks for execution based on their potential utility density, and completes them at specific times, in polynomialtime. We establish that CIC-VCUA achieves optimal timeliness during under-loads. Further, we identify the conditions under which timeliness assurances hold. Our simulation experiments illustrate CIC-VCUA's effectiveness and superiority.

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This paper describes the idea of embodied data objects. Using this concept, everyday objects can be used to represent bits and bytes of active information. These data objects can be used to interact with information-appliance-like devices that provide specific services as dictated by the context of interaction. The inherent affordances of physical artifacts are leveraged to make the interaction with these service-oriented devices intuitive and natural. We describe the idea of embodied data objects, followed by the design and implementation of two such service-oriented devices: a presentation projector and a printer.