Sugata Sanyal
School of Technology and Computer Science
Tata Institute of Fundamental Research, India
Email: sanyal@tifr.res.in
Rangarajan A. Vasudevan
Department of Computer Science and Engineering
Indian Institute of Technology, Madras, India
Email: ranga@cs.iitm.ernet.in
Ajith Abraham
Computer Science Department
Oklahoma State University, USA
Email: ajith.abraham@ieee.org
Marcin Paprzycki
Computer Science Department
Oklahoma State University, USA
Email: marcin@cs.okstate.edu

Abstract

Computational grids are believed to be the ultimate framework to meet the growing computational needs of the scientific community. Here, the processing power of geographically distributed resources working under different ownerships, having their own access policy, cost structure and the likes, is logically coupled to make them perform as a unified resource. The continuous increase of availability of high-bandwidth communication as well as powerful computers built of low-cost components further enhance chances of computational grids becoming a reality. However, the question of grid security remains one of the important open research issues. Here, we present some novel ideas about how to implement grid security, without appreciable performance degradation in grids. A suitable alternative to the computationally expensive encryption is suggested, which uses a key for message authentication. Methods of secure transfer and exchange of the required key(s) are also discussed.

Giuseppe Psaila Davide Brugali
Università degli Studi di Bergamo
Facoltà di Ingegneria
Viale Marconi 5
I-24044 Dalmine (BG), Italy
Email: psaila@unibg.it , brugali@unibg.it

Abstract

Knowledge discovery processes require powerful computational resources, and specific expertise to extract knowledge from large amounts of data. Data, resources, and expertise are now available on the Internet. Thus, decentralization of knowledge discovery processes seems a viable solution. However, effective use of the Internet calls for technologies which allow distributed resources to be flexibly combined, and their activities coordinated.
In a seminal paper, we introduced the concept of Decentralized Knowledge Discovery. In this paper, we discuss issues concerning the decentralized execution of knowledge discovery activities. We show that data and computational resources can be assembled together through the Internet to build a virtual database for Decentralized Knowledge Discovery. In particular, we point out which issues are relevant (and must be investigated) for building such systems.

Integrating digital information for coastal and marine sciences

Fausto Marincioni*, Frances L. Lightsom, Rebecca L. Riall, Guthrie A. Linck, Thomas C. Aldrich and Michael J. Caruso**

*Department of Earth and Environmental Science
Long Island University - C. W. Post Campus
720 Northern Boulevard
Brookville, New York 11548
Email: fausto.marincioni@liu.edu

U.S. Geological Survey
Coastal and Marine Geology Program
384 Woods Hole Road, Woods Hole, MA 02543-1598
Email: flightsom@usgs.gov

**Woods Hole Oceanographic Institution
Woods Hole, MA 02543-1050
Email: mcaruso@whoi.edu

Abstract

A pilot distributed geolibrary, the Marine Realms Information Bank (MRIB), was developed by the U.S. Geological Survey Coastal and Marine Geology Program and the Woods Hole Oceanographic Institution, to classify, integrate, and facilitate access to scientific information about oceans, coasts, and lakes. The MRIB is composed of a categorization scheme, a metadata database, and a specialized software backend, capable of drawing together information from remote sources without modifying their original format or content. Twelve facets are used to classify information: location, geologic time, feature type, biota, discipline, research method, hot topics, project, agency, author, content type, and file type. The MRIB approach allows easy and flexible organization of large or growing document collections for which centralized repositories would be impractical. Geographic searching based on the gazetteer and map interface is the centerpiece of the MRIB distributed geolibrary. The MRIB is one of a very few digital libraries that employ georeferencing -- a fundamentally different way to structure information from the traditional author/title/subject/keyword approach employed by most digital libraries. Lessons learned in developing the MRIB will be useful as other digital libraries confront the challenges of georeferencing.
 

CHANGE DETECTION IN XML DOCUMENTS FOR FIXED STRUCTURES USING EXCLUSIVE-OR (XOR)

Latifur Khan, Qing Chen, and Lei Wang
Department of Computer Science
University of Texas at Dallas
Richardson, TX 75083-0688
Email: [lkhan, qingch, leiwang]utdallas.edu


Abstract

XML is an emerging standard for the representation and exchange of internet data. The characteristics of xml, tree-structured (i.e. a collection of nodes) and self-descriptive, facilitate the detection of changes in an xml document in minute detail and at a finer grain than obtainable at the document level. Furthermore, for a fixed schema (structure) changes may frequently happen in the content or data values of xml documents in the web. We wish to propose a method that effectively detects this content or data value changes. Rather than inspecting all nodes between two versions of xml documents, we propose an effective algorithm, called top-down, which will detect changes in xml documents by exploring a subset of nodes in the tree. We would like to be certain that if a leaf node changes the algorithm will detect these changes, not only by inspecting the node itself, but also its parent node, grand parent node, and so on. For this, a signature for each node will be constructed which is basically an abstraction of the information stored in a node. There are several ways we can construct such a signature. We will choose exclusive-or (xor) to construct node signatures which will prevent a user from getting irrelevant information/change and make certain that the user does not miss relevant information. Note that for the web, along with being able to access huge quantities of information, the relevancy of information/change is more important than missing of relevant information/change. For this, in this paper we propose an automatic change detection algorithm which will identify changes between two versions of an xml document based on these signatures using xor. Our proposed algorithm will traverse the least number of nodes necessary to detect these changes. We demonstrate that our algorithm outperforms the traditional algorithm which exhaustively searches the entire space. We will also demonstrate analytically and empirically that the miss of relevant change is within tolerable range.

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