Context awareness enables applications to adapt themselves to their computing environment in order to better suit the needs of the user and the tasks. This paper describes a general middleware infrastructure for context collection and dissemination, realized as a Context Service. By way of two example applications, this paper also illustrates how context information provided by our context service can be exploited to enhance the user experience. These two applications are built upon the abstraction provided by the Context Service and thus help validate the design of this service. The first application, a Notification Dispatcher, uses context to route messages to the most appropriate communication device for a recipient. The second application, a context-aware content distribution system, uses context to predict users' access to web content, and uses these predictions to pre-process and pre-distribute content in order to reduce the access latency.

We address a single‐machine scheduling problem in which penalties are assigned for early and tardy completion of jobs. These penalties are common in industrial settings where early job completion can cause the cash commitment to resources in a time frame earlier than needed, giving rise to early completion penalties. Tardiness penalties arise from a variety of sources, such as loss of customer goodwill, opportunity costs of lost sales, and direct cash penalties. Accounting for earliness cost makes the performance measure nonregular, and this nonregularity has apparently discouraged researchers from seeking solutions to this problem. We found that it is not much more difficult to design an enumerative search for this problem than it would be if the performance measure were regular. We present and demonstrate an efficient timetabling procedure which can be embedded in an enumerative algorithm allowing the search to be conducted over the domain of job permutations.© 1993 John Wiley & Sons, Inc.

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