Showing papers by "Ramez Elmasri published in 2002"

Optimizing clustering algorithm in mobile ad hoc networks using genetic algorithmic approach

Abstract: We show how genetic algorithms can be useful in enhancing the performance of clustering algorithms in mobile ad hoc networks In particular, we optimize our recently proposed weighted clustering algorithm (WCA) The problem formulation along with the parameters are mapped to individual chromosomes as input to the genetic algorithmic technique Encoding the individual chromosomes is an essential part of the mapping process; each chromosome contains information about the clusterheads and the members thereof, as obtained from the original WCA The genetic algorithm then uses this information to obtain the best solution (chromosome) defined by the fitness function The proposed technique is such that each clusterhead handles the maximum possible number of mobile nodes in its cluster in order to facilitate the optimal operation of the medium access control (MAC) protocol Consequently, it results in the minimum number of clusters and hence clusterheads Simulation results exhibit improved performance of the optimized WCA than the original WCA Moreover, the loads among clusters are more evenly balanced by a factor of ten

Conceptual modeling for customized XML schemas

Abstract: XML was initially developed for document management, but it is becoming increasingly used for storing and exchanging all kinds of data on the Internet. In this paper, we introduce a design methodology for XML schemas that is based upon well-understood conceptual modeling methodologies. Because XML is hierarchical (tree-structured), many different XML schemas (or document structures) can be generated from the same conceptual database schema. We describe algorithms for generating customized hierarchical views from EER model, creating XML schemas from hierarchical views, and creating XML instance documents.

Conceptual Modeling for Customized XML Schemas

Abstract: XML was initially developed for document management, but it is becoming increasingly used for storing and exchanging all kinds of data on the Internet. In this paper, we introduce a design methodology for XML schemas that is based upon well-understood conceptual modeling methodologies. Because XML is hierarchical (tree-structured), many different XML schemas (or document structures) can be generated from the same conceptual database schema. We describe algorithms for generating customized hierarchical views from EER model, creating XML schemas from hierarchical views, and creating XML instance documents.

Using Smodels (declarative logic programming) to verify correctness of certain active rules

Abstract: In this paper we show that the language of declarative logic programming (DLP) with answer sets and its extensions can be used to specify database evolution due to updates and active rules, and to verify correctness of active rules with respect to a specification described using temporal logic and aggregate operators. We classify the specification of active rules into four kind of constraints which can be expressed using a particular extension of DLP called Smodels. Smodels allows us to specify the evolution, to specify the constraints, and to enumerate all possible initial database states and initial updates. Together, these can be used to analyze all possible evolution paths of an active database system to verify if they satisfy a set of given constraints.