Data Management in the APPA System

International audienceCombining Grid and P2P technologies can be exploited to provide high-level data sharing in large-scale distributed environments. However, this combination must deal with two hard problems: the scale of the network and the dynamic behavior of the nodes. In this paper, we present our solution in APPA (Atlas Peer-to-Peer Architecture), a data management system with high-level services for building large-scale distributed applications. We focus on data availability and data discovery which are two main requirements for implementing large-scale Grids. We have validated APPA's services through a combination of experimentation over Grid5000, which is a very large Grid experimental platform, and simulation using SimJava. The results show very good performance in terms of communication cost and response time

Survey of data replication in P2P systems

Large-scale distributed collaborative applications are getting common as a result of rapid progress in distributed technologies (grid, peer-to-peer, and mobile computing). Peer-to-peer (P2P) systems are particularly interesting for collaborative applications as they can scale without the need for powerful servers. In P2P systems, data storage and processing are distributed across autonomous peers, which can join and leave the network at any time. To provide high data availability in spite of such dynamic behavior, P2P systems rely on data replication. Some replication approaches assume static, read-only data (e.g. music files). Other solutions deal with updates, but they simplify replica management by assuming no update conflicts or single-master replication (i.e. only one copy of the replicated data accepts write operations). P2P advanced applications, which must deal with semantically rich data (e.g. XML documents, relational tables, etc.) using a high-level SQL-like query language, are likely to need more sophisticated capabilities such as multi-master replication (i.e. all replicas accept write operations) and update conflict resolution. These issues are addressed by optimistic replication. Optimistic replication allows asynchronous updating of replicas so that applications can progress even though some nodes are disconnected or have failed. As a result, users can collaborate asynchronously. However, concurrent updates may cause replica divergence and conflicts, which should be reconciled. In this survey, we present an overview of data replication, focusing on the optimistic approach that provides good properties for dynamic environments. We also introduce P2P systems and the replication solutions they implement. In particular, we show that current P2P systems do not provide eventual consistency among replicas in the presence of updates, apart from APPA system, a P2P data management system that we are building

The role of emotional variables in the classification and prediction of collective social dynamics

We demonstrate the power of data mining techniques for the analysis of collective social dynamics within British Tweets during the Olympic Games 2012. The classification accuracy of online activities related to the successes of British athletes significantly improved when emotional components of tweets were taken into account, but employing emotional variables for activity prediction decreased the classifiers' quality. The approach could be easily adopted for any prediction or classification study with a set of problem-specific variables.Comment: 16 pages, 9 figures, 2 tables and 1 appendi

Measurement of performance using acceleration control and pulse control in simulated spacecraft docking operations

Nine commercial airline pilots served as test subjects in a study to compare acceleration control with pulse control in simulated spacecraft maneuvers. Simulated remote dockings of an orbital maneuvering vehicle (OMV) to a space station were initiated from 50, 100, and 150 meters along the station's -V-bar (minus velocity vector). All unsuccessful missions were reflown. Five way mixed analysis of variance (ANOVA) with one between factor, first mode, and four within factors (mode, bloch, range, and trial) were performed on the data. Recorded performance measures included mission duration and fuel consumption along each of the three coordinate axes. Mission duration was lower with pulse mode, while delta V (fuel consumption) was lower with acceleration mode. Subjects used more fuel to travel faster with pulse mode than with acceleration mode. Mission duration, delta V, X delta V, Y delta V., and Z delta V all increased with range. Subjects commanded the OMV to 'fly' at faster rates from further distances. These higher average velocities were paid for with increased fuel consumption. Asymmetrical transfer was found in that the mode transitions could not be predicted solely from the mission duration main effect. More testing is advised to understand the manual control aspects of spaceflight maneuvers better

A conditional role-involved purpose-based access control model

This paper presents a role-involved conditional purpose-based access control (RCPBAC) model, where a purpose is defined as the intension of data accesses or usages. RCPBAC allows users using some data for certain purpose with conditions. The structure of RCPBAC model is defined and investigated. An algorithm is developed to achieve the compliance computation between access purposes (related to data access) and intended purposes (related to data objects) and is illustrated with role-based access control (RBAC) to support RCPBAC. According to this model, more information from data providers can be extracted while at the same time assuring privacy that maximizes the usability of consumers' data. It extends traditional access control models to a further coverage of privacy preserving in data mining environment as RBAC is one of the most popular approach towards access control to achieve database security and available in database management systems. The structure helps enterprises to circulate clear privacy promise, to collect and manage user preferences and consent

Risk assessment, and carcinogen mutagen for workers potentially exposed in the research laboratories of “Sapienza” University of Rome for Health Surveillance

The following work is meant to represent the evaluation of risk factors for the health of exposed workers, arising from the management of carcinogenic and mutagenic substances, through the use of algorithms. In some places of work as a research laboratory, it is more suitable a theoretical and practical methodology (algorithm) which allows a "timely" exposure assessment. The methodology developed and used is able to determine the level of risk of exposure due to a single agent and / or to more agents. Results obtained by the algorithm, have shown an higher exposure to 1 for formaldehyde (Lcanc = 1.32), while for acrylamide results obtained shows a lower exposure to 1 (Lcanc = 0.528). Although the overall exposure level of studied workers higher value to 1 (Lcanc= 1.848), the Occupational Medicine Centre of "Sapienza" - University of Rome, in agreement with the position taken by the Italian Society of Occupational Medicine and Industrial Hygiene applies health surveillance even in the presence of potential health risk reducing it among the general protection measures the health and safety of workers