18174475
Implication Problems for Functional Constraints on Databases Supporting Complex Objects
Virtually all semantic or object-oriented data models assume that objects have an identity separate from any of their parts and allow uses to define complex object types in which part values may be any other objects. In G. E. Weddell (ACM Trans. Database Systems17, No. 1 (1992), 32-64), a more general form of functional dependency is proposed for such models in which component attributes may correspond to descriptions of property paths, called path functional dependencies (PFDs). The main contribution of the reference is a sound and complete axiomatization for PFDs when databases may be infinite. However, a number of issues were left open which are resolved in this paper. We first prove that the same axiomatization remains complete if PFDs are permitted empty left-hand sides, but that this is not true if logical consequence is defined with respect to finite databases. We then prove that the implication problem for arbitrary PFDs is decidable. The proof suggests a means of characterizing an important function closure which is then used to derive an effective procedure for constructing a deterministic finite state automaton representing the closure. The procedure is further refined to efficient polynomial time algorithms for the implication problem for cases in which antecedent PFDs are a form of complex key constraint.
17923888
A personal tourism navigation system to support traveling multiple destinations with time restrictions
We propose a personal navigation system (called PNS) which navigates a tourist through multiple destinations efficiently. In our PNS, a tourist can specify multiple destinations with desired arrival/stay time and preference degree. The system calculates the route including part of the destinations satisfying tourist's requirements and navigates him/her. For the above route search problem, we have developed an efficient route search algorithm using a genetic algorithm. We have designed and implemented the PNS as a client-server system so that the portable device users can use the PNS through the Internet. Experiments using general map data and PDAs show that our PNS can calculate a semioptimal route almost in real-time.
7202623
An Energy-Aware Video Streaming System for Portable Computing Devices
In this demonstration, we show an energy-aware video streaming system which allows users to play back video for the specified duration within the remaining battery amount. In the system, we execute a proxy server on an intermediate node in the network. It receives the video stream from a content server, transcodes it to the videos with appropriate quality, and forwards it to a PDA or a laptop PC. Here, suitable parameter values of the video (such as picture size, frame rate and bitrate) which enable playback for the specified duration are automatically calculated on the proxy using our battery consumption model. The system also allows users to play back video segments with different qualities based on the importance specified to each video segment.
42397815
Implication Problems for Functional Constraints on Databases Supporting Complex Objects
7115154
MTcast: Robust and Efficient P2P-Based Video Delivery for Heterogeneous Users
In this paper, we propose a new video delivery method called MTcast (Multiple Transcode based video multicast) which achieves efficient simultaneous video delivery to multiple users with different quality requirements by relying on user nodes to transcode and forward video to other user nodes. In MTcast, each user specifies a quality requirement for a video consisting of bitrate, picture size and frame rate based on the user's environmental resource limitation. All users can receive video with the specified quality (or near this quality) along a single delivery tree. The main characteristics of MTcast are in its scalability, high user satisfaction degree in received video quality, short startup latency and robustness against node failure. Through simulations, we have confirmed that MTcast can achieve much higher user satisfaction degree and robustness against node failure than the layered multicast method.
28724522
On the possibility of path expressions containing backward navigations in object-oriented databases
5334322
Performance analysis of disk allocation method using error-correcting codes
The problem of distributing a Cartesian product file on multiple disks to maximize the parallelism for partial match queries is addressed. C. Faloutsos et al. (1989) have proposed an allocation method for Cartesian product files on multiple disks by using linear error-correcting codes. The performance of the allocation method is analyzed. Some conditions under which the allocation method is strictly optimal for queries with a given number of unspecified attributes are presented. A necessary and sufficient condition for a linear code to give a strictly optimal allocation method is discussed. Formulas for the average response time on queries with w unspecified attributes, denoted T/sub w/, in terms of the weight distribution of the code or its dual code, and formulas for the average response time Ton all queries, are given. Several examples whose average response times T/sub w/ or T are close to theoretical lower bounds are presented. >
14842083
The network communities of SeniorNet
With the explosion of participation on the Internet, there is increasing interest and speculation in extending its uses to support diverse online communities, and particular interest in using the Internet to combat loneliness and isolation amongst senior citizens For the past year, we have been investigating SeniorNet (SN), a 12 year old organization that attempts to bring seniors together via computer networking technologies. We found a rich tapestry of human relationships supported by various technical and social underpinnings. In this paper, we delve into the richness of an active community and describe the intertwining technical and social factors that make it valuable and useful for its members. An underlying question in these discussions is "If network communities have to be principally created and maintained by their members (as we posit), then how do designers help without getting in the way?".
5523130
Design for network communities
Collaboration has long been of considerable interest in the CHI community. This paper proposes and explores the concept of network communities as a crucial part of this discussion. Network communities are a form of technologymediated environment that foster a sense of community among users. We consider several familiar systems and describe the shared characteristics these systems have developed to deal with critical concerns of collaboration. Based on our own experience as designers and users of a variety of network communities. we extend this initial design space along three dimensions: the articulation of a persistent sense of location, the boundary tensions between real and virtual worlds, and the emergence and evolution of community.
45793732
Adaptive Robust Super-exponential Algorithms for Deflationary Blind Equalization of Instantaneous Mixtures
The so called “super-exponential” algorithms (SEA’s) are attractive algorithms for solving blind signal processing problems. The conventional SEA’s, however, have such a drawback that they are very sensitive to Gaussian noise. To overcome this drawback, we propose a new SEA. While the conventional SEA’s use the second- and higher-order cumulants of observations, the proposed SEA uses only the higher-order cumulants of observations. Since higher-order cumulants are insensitive to Gaussian noise, the proposed SEA is robust to Gaussian noise, which is referred to as a robust super-exponential algorithm (RSEA). The proposed RSEA is implemented as an adaptive algorithm, which is referred to as an adaptive robust super-exponential algorithm (ARSEA). To show the validity of the ARSEA, some simulation results are presented.
31816332
Source location problems considering vertex-connectivity and edge-connectivity simultaneously
Let G = (V, E) be an undirected multigraph, where V and E are a set of vertices and a set of edges, respectively. Let k and l be fixed nonnegative integers. This paper considers location problems of finding a minimum-size vertex-subset S ⊆ V such that for each vertex x ∈ V the vertex-connectivity between S and x is greater than or equal to k and the edge-connectivity between S and x is greater than or equal to l. For the problem with edge-connectivity requirements, that is, k = 0, an O(L(|V|, |E|, l)) time algorithm is already known, where L(|V|, |E|, l) is the time to find all h-edge-connected components for h = 1, 2, … , l and O(L(|V|, |E|, l)) = O(|E| + |V|2 + |V|min{|E|, l|V|}min{l, |V|}) is known. In this paper, we show that the problem with k ≥ 3 is NP-hard even for l = 0. We then present an O(L(|V|, |E|, l)) time algorithm for 0 ≤ k ≤ 2 and l ≥ 0. Moreover, we prove that the problem parameterized by the size of S is fixed-parameter tractable (FPT) for k = 3 and l ≥ 0. © 2002 Wiley Periodicals, Inc.