193488
Synchronized Disk Interleaving
A group of disks may be interleaved to speed up data transfers in a manner analogous to the speedup achieved by main memory interleaving. Conventional disks may be used for interleaving by spreading data across disks and by treating multiple disks as if they were a single one. Furthermore, the rotation of the interleaved disks may be synchronized to simplify control and also to optimize performance. In addition, check- sums may be placed on separate check-sum disks in order to improve reliability. In this paper, we study synchronized disk interleaving as a high-performance mass storage system architecture. The advantages and limitations of the proposed disk interleaving scheme are analyzed using the M/G/1 queueing model and compared to the conventional disk access mechanism.
20698705
Home health care support
We describe an ap@ication to interconnect health care providers and thew patients in the home. The application includes information services, symptom analy SIS, ~idance in the performance of procedures, emotmnal support, and communications among the health care providers, patients and caretakers.
6041360
Modeling timed user-interactions in multimedia documents
Interactive multimedia documents (or systems) can be characterized by active user participation and the diversity of multimedia information accessed at various levels of granularity. They need to support extensive user participation in selecting and tailoring the information and its presentation. Multimedia information fragments may vary from portions of video, pieces of audio, newspaper quotations or chapters of a book. Effectively managing the creation, evolution and complexity of multimedia documents formed by combining media fragments is an essential capability. We consider the hyperstory model of a multimedia document, where a document is structured hierarchically in three dimensions: time, space and asynchrony. The model provides a layered approach in structuring multimedia documents, thus reducing the complexities of large systems. The hyperstory model supports user interactions that are timed, and also supports preemptive resuming. Timed user interactions with the document are modeled with a newly introduced timed Petri-net (TPN*). TPN* is used to infer the behavior of the system. This paper describes TPN*'s modeling and analysis and its application to the hyperstory model.
18630917
Multimedia documents with elastic time
Time is an essential component in interactive multimedia documents (or systems). We present the elastic time model for multimedia documents. Using the metaphor of a spring system, it allows authors to associate with each multimedia object a minimum and a maximum length and a length at rest. Authors can connect the (elastic) objects by de ning temporal relationships among them. If the given specication is consistent, a document is produced which is also elastic, with a minimum, a maximum, and an optimal length. As such, our elastic model associates with a document a range of feasible solutions in addition to an optimal one. The author can then select from the acceptable range an alternative length for the document, and the system will compute a revised solution that takes the additional global constraint into e ect. The system can answer questions, such as: \Can I show this multimedia presentation in 10 minutes? If so, how should all the objects be scheduled?" Furthermore, the system also takes fairness into consideration and distributes any necessary stretching or shrinking across multimedia objects contained in a document. As such, the elastic time model provides expressive power and exibility in document auThe author's current address is: University of Maryland, College Park, MD 20742, JUNESONG @ CS.UMD.EDU thoring and browsing. The proposed approach has been implemented in Smalltalk/OS2.
528361
Eliminating Bottlenecks in Overlay Multicast
Recently many overlay multicast systems have been proposed due to the limited availability of IP multicast. Because they perform multicast forwarding without support from routers, data may be delivered multiple times over the same physical link, causing a bottleneck. This problem is more serious for applications demanding high bandwidth such as multimedia distribution. Although such bottlenecks can be removed by changing overlay topology, a naive approach may create bottlenecks in other parts of the network. In this paper, We propose an algorithm that removes all bottlenecks caused by the redundant data delivery of overlay multicast, detecting such bottlenecks using a wavelet-based technique we recently proposed. In a case where the source rate is constant and the available bandwidth of each link is not less than the source rate, our algorithm guarantees that every node receives at the full source rate. Simulation results show that even in a network with a dense receiver population, our algorithm finds a tree that satisfies all the receiving nodes while other heuristic-based approaches often fail.
10136578
Tripodal schematic design of the control architecture for the Service Robot PSR
This paper describes a control architecture design and a system integration strategy for the autonomous service robot PSR (Public Service Robot). The PSR is under development at the KIST (Korea Institute of Science and Technology) for service tasks in public spaces such as office buildings and hospitals. The proposed control architecture is designed by tripodal frameworks, which are layered functionality diagram, class diagram, and configuration diagram. The tripodal schematic design clearly points out the way of integrating various hardware and software components. The developed strategy is implemented on the PSR and successfully tested.
61206461
A wavelet-based approach to detect shared congestion
Per-flow congestion control helps endpoints fairly and efficiently share network resources. Better utilization of network resources can be achieved, however, if congestion management algorithms can determine when two different flows share a congested link. Such knowledge can be used to implement cooperative congestion control or improve the overlay topology of a P2P system. Previous techniques to detect shared congestion either assume a common source or destination node, drop-tail queueing, or a single point of congestion. We propose in this paper a novel technique, applicable to any pair of paths on the Internet, without such limitations. Our technique employs a signal processing method, wavelet denoising, to separate queueing delay caused by network congestion from various other delay variations. Our wavelet-based technique is evaluated through both simulations and Internet experiments. We show that, when detecting shared congestion of paths with a common endpoint, our technique provides faster convergence and higher accuracy while using fewer packets than previous techniques, and that it also accurately determines when there is no shared congestion. Furthermore, we show that our technique is robust and accurate for paths without a common endpoint or synchronized clocks; more specifically, it can tolerate a synchronization offset of up to one second between two packet flows.
8582728
Automatic Inference of Structural Changes for Matching across Program Versions
Mapping code elements in one version of a program to corresponding code elements in another version is a fundamental building block for many software engineering tools. Existing tools that match code elements or identify structural changes - refactorings and API changes - between two versions of a program have two limitations that we overcome. First, existing tools cannot easily disambiguate among many potential matches or refactoring candidates. Second, it is difficult to use these tools' results for various software engineering tasks due to an unstructured representation of results. To overcome these limitations, our approach represents structural changes as a set of high-level change rules, automatically infers likely change rules and determines method-level matches based on the rules. By applying our tool to several open source projects, we show that our tool identifies matches that are difficult to find using other approaches and produces more concise results than other approaches. Our representation can serve as a better basis for other software engineering tools.
1994375
Effective Temporal Aggregation Using Point-Based Trees
Temporal databases introduce the concept of time into underlying data, and provide built-in facilities that allow users to store and retrieve time-varying data. The aggregation in temporal databases, that is, temporal aggregation is an extension of conventional aggregation on the domain and range of aggregates to include time concept. Temporal aggregation is important for various applications, but is very expensive. In this paper, we propose a new tree structure for temporal aggregation, called PA-tree, and aggregate processing method based on the PA-tree. We show that the time complexity of the proposed method is better than those of the existing methods. The time complexity of the proposed method is shown to be indeed the lower bound of the problem. We perform comparative experiments and show the performance advantage of our proposed method in practice.