We consider a single-server queueing system with Poisson arrivals and general service times. While the server is up, it is subject to breakdowns according to a Poisson process. When the server breaks down, we may either repair the server immediately or postpone the repair until some future point in time. The operating costs of the system include customer holding costs, repair costs and running ...

The performance of demand-driven caching is known to depend on the locality of reference exhibited by the stream of requests made to the cache. In spite of numerous efforts, no consensus has been reached on how to formalize this notion, let alone on how to compare streams of requests on the basis of their locality of reference. We take on this issue with an eye towards validating operational ex...

BACKGROUND In our institution, we have redefined our criteria for direct availability of red blood cell (RBC) units in the operation room. In this study, we sought to evaluate the safety of applying this new logistical policy of blood transfusion in the first preliminary group of patients. METHODS In March 2010, we started a new policy concerning the elective availability of RBC units in the ...

In systems with shared resources, authorization policy enforcement ensures that these resources are accessible only to users who are allowed to do so. Recently, there is growing interest to (i) extend authorization policy enforcement mechanisms provided by the operating system, and (ii) enable user-space servers to enforce authorization policies on their clients. A popular mechanism for authori...

Policy learning is an active topic in dialogue systems research, but it has not been explored in relation to Interactive Question Answering (IQA). We take a first step in learning adaptive interaction policies for QA: we address the question of how to acquire enough reliable query constraints, how many database results to present to the user and when to present them, given the competing trade-o...

To gain access to account privileges, an intruder masquerades as the proper account user. Information from user feedback helps to improve the accuracy of classifiers used for detecting masquerades. Instead of operating in isolation, the online sequential classifier can request feedback from the user. In the full-feedback policy, the classifier verifies every session; in the feedback-on-alarm po...

Large scale distributed applications combine network access with multiple storage and computational elements. The distributed responsibility for resource control creates new security issues, caused by the complexity of the operating environment. In particular, policies at multiple layers and locations force conventional mechanisms such as firewalls and compartmented file storage into roles wher...

A national knowledge management system consists of internal knowledge management systems of governmental agencies and various knowledge services playing a role of intermediary, catalyst, and network. A policy knowledge service plays the roles of abstracting, codifying, and diffusing knowledge in public sector. Through abstraction and codification, it maximizes the proprietary value of knowledge...