[Show abstract][Hide abstract] ABSTRACT: Stream grids are wide-area grid computing environments that are fed by a set of stream data sources, and Queries arrive at the grid from users and applications external to the system. The kind of queries considered in this work is long-running continuous LRC queries, which are neither short-lived nor infinitely long lived. The queries are "open" from the grid perspective as the grid cannot control or predict the arrival of a query with time, location, required data and query revocations. Query optimization in such an environment has two major challenges, i.e., optimizing in a multi-query environment and continuous optimization, due to new query arrivals and revocations. As generating a globally optimal query plan is an intractable problem, this work explores the idea of emergent optimization where globally optimal query plans emerge as a result of local autonomous decisions taken by the grid nodes. Drawing concepts from evolutionary game theory, grid nodes are modeled as autonomous agents that seek to maximize a self-interest function using one of a set of different strategies. Grid nodes change strategies in response to variations in query arrival and revocation patterns, which is also autonomously decided by each grid node.
MEDES '09: International ACM Conference on Management of Emergent Digital EcoSystems, Lyon, France, October 27-30, 2009; 01/2009
[Show abstract][Hide abstract] ABSTRACT: Multi-stream interactive systems can be seen as \hidden adversary" systems (HAS), where the observable behaviour on any interaction channel is afiected by interactions happening on other channels. One way of modelling HAS is in the form of a multi-process I/O automata, where each interacting process appears as a token in a shared state space. Constraints in the state space specify how the dynamics of one process afiects other processes. We deflne the \liveness criterion" of each process as the end objective to be achieved by the process. The problem now for each process is to achieve this objective in the face of unforeseen interferences from other processes. In an earlier paper, it was proposed that this uncertainty can be mitigated by collaboration among the disparate processes. Two types of collaboration philosophies were also suggested: altruistic collaboration and pragmatic collaboration. This paper addresses the HAS validation problem where processes collaborate altruistically.
[Show abstract][Hide abstract] ABSTRACT: WAND is a P2P meta-data management system providing a file-system tree interface. Users are able to share files on the global
file-system tree. The file system tree is robust and maintains its structure even when nodes enter and leave the network.
The key ideas that make the file-system tree robust are a concept of virtual folders and a novel algorithm to handle network partitioning.
Distributed Computing and Internet Technology, 4th International Conference, ICDCIT 2007, Bangalore, India, December 17-20, Proceedings; 01/2007
[Show abstract][Hide abstract] ABSTRACT: Large information systems (IS) comprise of several independent applications that share a common set of resources and data. Usually, there are implicit and subtle dependencies across these applications that are not specifically captured. This is especially so if the applications are bought off the shelf or are developed by independent third parties. Dependencies or global semantic constraints are difficult to discern and incorporate into the design of individual software components. Global constraints may change over time and it is usually expensive or infeasible to change individual application logic in every such situation. In order to address such an issue, we propose LogicFence, a framework that accepts a definition of global constraints and translates these constraints into primitives that are embedded into the run-time environments of application programs (currently, into the JVM of Java applications). LogicFence monitors the state of application programs and prevents the disparate instances to collectively form a globally inconsistent state
Tenth International Database Engineering and Applications Symposium (IDEAS 2006), 11-14 December 2006, Delhi, India; 01/2006
[Show abstract][Hide abstract] ABSTRACT: A new architecture for scheduling an open-ended set of medical post processing applications in clusters is described in this work. The scheduler takes into consideration the characteristics of the set of currently executing applications as well as the incoming request to ensure optimal application performance. The approach uses a feedback mechanism to learn the resource requirements of an application and is non-intrusive. The scheduler is not tightly coupled with the applications and therefore can schedule an open-ended set of applications.
[Show abstract][Hide abstract] ABSTRACT: WAND is a meta-data management system that provides a file-system tree for users of an internet based P2P network. The tree is robust and retains its structure even when nodes (peers) enter and leave the network. The robustness is based on a concept of virtual folders that are automatically created to retain paths to lower level folders whenever a node hosting a higher-level folder moves away. Other contributions of the WAND system include its novel approach towards managing root directory information and handling network partitions.
Proceedings of the 14th international conference on World Wide Web, WWW 2005, Chiba, Japan, May 10-14, 2005 - Special interest tracks and posters; 01/2005