16000193
Cheat detection for MMORPG on P2P environments
In this paper, we propose a new method for detecting cheat in P2P-based MMORPG. We suppose a typical P2P-based event delivery architecture where the entire game space is divided into subareas and a responsible node (selected from player terminals) delivers each event happened in the sub-area to player nodes there every predetermined time interval called timeslot. In the proposed method, we introduce multiple monitor nodes (selected from player terminals) which monitor the game state and detect cheat when it happens. In order to allow monitor nodes to track the correct game states for the corresponding subarea, we let monitor nodes and a responsible node retain a random number seed and player nodes send their events not only to responsible node but also monitor nodes so that the monitor nodes and the responsible node can uniquely calculate the latest game state from the previous game state and game events which happened during the current timeslot. Either responsible node, monitor nodes or player nodes can detect cheat by comparing hash values of game state which are retained by those nodes periodically, and role back events happened since the last correct game state. Through experiments in PlanetLab, we show that our method achieves practical performance to detect cheats.
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.
28724522
On the possibility of path expressions containing backward navigations in object-oriented databases
42397815
Implication Problems for Functional Constraints on Databases Supporting Complex Objects
5990559
A Method to Plan Group Tours with Joining and Forking
Group sightseeing has some advantages in terms of required budget and so on. Some travel agents provide package tours of group sightseeing, but participants have to follow a predetermined schedule in tour, and thus there may be no plan which perfectly satisfies the tourist's expectation. In this paper, we formalize a problem to find group sightseeing schedules for each user from given users' preferences and time restrictions corresponding to each destination. We also propose a Genetic Algorithm-based algorithm to solve the problem. We implemented and evaluated the method, and confirmed that our algorithm finds efficient routes for group sightseeing.
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.
23108457
On directable nondeterministic trapped automata
A finite automaton is said to be directable if it has an input word, a directing word, which takes it from every state into the same state. For nondeterministic (n.d.) automata, directability can be generalized in several ways. In [8], three such notions, D1-, D2-, and D3-directability, are introduced. In this paper, we introduce the trapped n.d. automata, and for each i = 1, 2, 3, present lower and upper bounds for the lengths of the shortest Di-directing words of n-state Di-directable trapped n.d. automata. It turns out that for this special class of n.d. automata, better bounds can be found than for the general case, and some of the obtained bounds are sharp.
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?".
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.
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. >
32882610
Membership Problems for Data Dependencies in Relational Expressions
In relational databases, a query can be formulated in terms of a relational algebra expression using projection, selection, restriction, cross product and union. In this paper, we consider a problem, called the membership problem, of determining whether a given dependency d is valid in a given relational expression E over a given database scheme R that is, whether every instance of the view scheme defined by E satisfies d (assuming that the underlying constraints in R are always satisfied). 
 
Consider the case where each relation scheme in R is associated with functional dependencies (FDs) as constraints, and d is an FD. Then the complement of the membership problem is NP-complete. However, if E contains no union, then the membership problem can be solved in polynomial time. Furthermore, if E contains neither a union nor a projection, then we can construct in polynomial time a cover for valid FDs in E, that is, a set of FDs which implies every valid FD in E. 
 
Consider the case where each relation scheme in R is associated with multivalued dependencies (MVDs) as well as FDs, and d is an FD or an MVD. Even if E consists of selections and cross products only, the membership problem is NP-hard. However, if E contains no union, and each relation scheme name in R occurs in E at most once, then the membership problem can be solved in polynomial time. As a corollary of this result, it can be determined in polynomial time whether a given FD or MVD is valid in R1⋈⋯⋈Rs, where R1,…,Rs are relation schemes with FDs and MVDs, and Ri⋈Rj is the natural join of Ri and Rj.