Most data managed by existing, real-world database applications is time referenced. Often, two temporal aspects of data are of interest, namely valid time, when data is true in the mini-world, and transaction time, wh...
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Most data managed by existing, real-world database applications is time referenced. Often, two temporal aspects of data are of interest, namely valid time, when data is true in the mini-world, and transaction time, when data is current in the database, resulting in so-called bitemporal data. Like spatial data, bitemporal data thus has associated two-dimensional regions. Such data is in part naturally now-relative: some data is true until the current time, and some data is part of the current database state. So, unlike for spatial data, bitemporal data regions may grow continuously. Existing indices, e.g., B+- and R-trees, typically do not contend well with even small amounts of now-relative data. In contrast, the 4-R index presented in the paper is capable of indexing general bitemporal data efficiently. the different kinds of growing data regions are transformed into stationary regions, which are then indexed by R*-trees. Queries are also transformed to counter the data transformations, yielding a technique with perfect precision and recall. Performance studies indicate that the technique is competitive withthe best existing index;and unlike this existing index, the new technique does not require extension of the DBMS kernel.
In a previous paper, we described a system called STAGS (Storage Access Coordination System) for High Energy and Physics (HEP) experiments. these experiments generate very large volumes of "event" data at a ...
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In a previous paper, we described a system called STAGS (Storage Access Coordination System) for High Energy and Physics (HEP) experiments. these experiments generate very large volumes of "event" data at a very high rate. the volumes of data may reach 100's of terabytes/year and therefore they are stored on robotic tape systemsthat are managed by a mass storage system. the data are stored as files on tapes according to a predetermined order, usually according to the order they are generated. A major bottleneck is the retrieval of subsets of these large datasets during the analysis phase. STAGS is designed to optimize the use of a disk cache, and thus minimize the number of files read from tape. In this paper, we describe an interesting problem of disk staging coordination that goes beyond the one-file-at-a-time requirement. the problem stems from the need to coordinate the simultaneous caching of groups of files that we refer to as "bundles of files". All files from a bundle need to be at the same time in the disk cache in order for the analysis application to proceed. this is a radically different problem from the case where the analysis applications need only one file at a time. In this paper, we describe the method of identifying the file bundles, and the scheduling of bundle caching in such a way that files shared between bundles are not removed from the cache unnecessarily. We describe the methodology and the policies used to determine the order of caching bundles of files, and the order of removing files from the cache when space is needed.
Proposes a very small on-chip multimedia real-time operating system (OS) for embedded system LSIs and demonstrates its usefulness on MPEG-2 multimedia applications. the real-time OS, which has a new cyclic task with &...
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We present an approach to static priority preemptive process scheduling for the synthesis of hard real-time distributed embeddedsystems where communication plays an important role. the communication model is based on...
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More and more, society depends on computer based technical systems, which are being applied for both control and automation functions under realtime constraints. these so-called "embedded computer systemsii"...
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this paper introduces an implementation of a clock synchronization method for NTP (Network time Protocol). NTP is widely used and an effective application protocol in maintaining time synchronization over the network....
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the proceedings contain 74 papers. the topics discussed include: software dependability considered as the main problem of contemporary realtimecomputing;state restoration in real-timesystems;dynamic adjustment of s...
ISBN:
(纸本)0769503063
the proceedings contain 74 papers. the topics discussed include: software dependability considered as the main problem of contemporary realtimecomputing;state restoration in real-timesystems;dynamic adjustment of serialization order using timestamp intervals in real-time databases;value-driven multi-class overload management;adaptive data broadcast strategy for transactions with multiple data requests in mobile computing environments;a framework for scheduling in safety-critical embedded control systems;feasibility intervals for the deadline driven scheduler with arbitrary deadlines;scheduling periodic task systems to minimize output jitter;adaptive bandwidth reservation for multimedia computing;and pipeline timing analysis using a trace-driven simulator.
Low power and energy consumption will always be an essential requirement in many real-timeembeddedapplications. Voltage scaling is a relatively novel approach to reducing energy consumption. the idea is that a proce...
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A VLSI architecture of a real-time wavelet video coder is described, withthe main focus put on the efficient VLSI implementation and scalable code generation. To achieve this goal, this architecture devises a modifie...
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In the development of embedded hard real-timesystemsthe ability to guarantee worst case execution times is gaining importance and complexity. the fast evolving processor acceleration techniques constantly increase t...
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