Ghassan Z. Qadah

Learning Styles of Computer Programming Students: A Middle Eastern and American Comparison

Although there are many studies addressing the relationship of learning style to outcomes in engineering courses, few have attempted direct cross-cultural comparisons. This study investigates similarities and differences in the learning styles of computer science and engineering students at a Middle Eastern institution and an American university in the Midwestern United States. Comparative data on student learning style profiles and course outcomes suggest that, despite vast cultural differences, strong similarities exist between learning styles of these students. Seemingly, a consistent pattern in how these students learn across cultures also exists. These findings have significant implications for the creation of globally effective teaching materials

The join algorithms on a shared-memory multiprocessor database machine

The authors develop and present a large set of parallel algorithms for implementing the join operation on a shared-memory multiprocessor database machine. The development of these algorithms follows a structured approach. The major steps involved in the processing of the join operation by the machine are first identified. Then, alternative join algorithms are constructed by concatenating the different ways of performing these steps. A study of the performance of the proposed algorithms is presented. This study shows, among other things, that for a given hardware configuration there is not just one overall best performing join algorithm, but rather different algorithms score the best performance, depending on the characteristics of the data participating in the join operation. >

Efficient algorithms for the instantiated transitive closure queries

The performances of several algorithms suitable for processing an important class of recursive queries called the instantiated transitive closure (TC) queries are studied and compared. These algorithms are the wavefront, delta -wavefront, and a generic algorithm called super-TC. During the evaluation of a TC query, the first two algorithms may read a given disk page more than once, whereas super-TC reads the disk page at most once. A comprehensive performance evaluation of these three algorithms using rigorous analytical and simulation models is presented. The study reveals that the relative performance of the algorithms is a strong function of the parameters which characterize the processed TC query and the relation referenced by that query. The superiority of one of the super-TC variants over all of the other presented algorithms is shown. >

The Processing and Evaluation of Transitive Closure Queries

A transitive closure operator will be an important new operator in future deductive database systems. We discuss the compilation of recursive rule clusters into formulas containing transitive closure operations and study three promising algorithms for the processing of transitive closure queries: the wavefront algorithm, the δ-wavefront algorithm and the level-relaxed δ-wavefront algorithm. The relative processing efficiency of these algorithms are analyzed and compared based on different database structures and accessing methods. Our study shows that the δ-wavefront algorithm performs consistently better than the wavefront algorithm, and the level-relaxed δ-wavefront algorithm has high potential of further reducing I/O accessing cost on the databases with clustered derivation paths. The study also provides some interesting heuristics on the database structures and implementation techniques in the processing of recursive database queries.

Semantic query reformulation in deductive databases

A method is proposed for identifying relevant integrity constraints (ICs) for queries involving joins/unions of base relations and defined relations by use of graphs. The method does not rely on heavy preprocessing or redundancy. To effectively select those ICs that are relevant to a given query, the relationship between the predicates in the query is identified using an AND/OR tree where an AND mode represents a join operation and an OR node represents a union operation. Ways of collecting ICs are described that are not directly related to the query but can be useful in query optimization.<<ETX>>

The Equi-Join Operation on a Multiprocessor Database Machine: Algorithms and the Evaluation of their Performance

The equi-join operation is one of the most important operations of the relational data model. It participates in all queries which reference more than one relation. In this paper, a large set of parallel algorithms for implementing the equi-join operation on a multiprocessor database machine called MIRDM (MIchigan Relational Database Machine), is presented. An outline of a study for the performance of the proposed algorithms in carrying out the equi-Join operation on MIRDM, is also presented. The main objective of this study is twofold: the determination of the overall best performing equi-join algorithm and the investigation of the effectiveness (from the equi-join operation point of view) of performing some tuning to the architecture of MIRDM. This study shows, among others, that for a given MIRDM configuration; the overall best performing equi-join algorithm is not unique and different algorithms score the best performance depending on the characteristics of the data participating in the equi-join operation.

The efficient computation of strong partial transitive-closures

The development of efficient algorithms to process the different forms of transitive-closure queries within the context of large database systems has attracted a large volume of research efforts. The authors present a new algorithm that is suitable for processing one of these forms, the strong partially instantiated query, in which one of the querys arguments is instantiated to a set of constants. The processing of this algorithm yields a set of tuples that draw their values from both of the querys instantiated and uninstantiated arguments. This algorithm avoids the redundant computations and the high storage costs found in a number of similar algorithms.<<ETX>>

Filter-Based Join Algorithms on Uniprocessor and Distributed-Memory Multiprocessor Database Machines

The hybrid-hash algorithm and its parallel variant have been recently found to outperform all other algorithms in joining disk-based large relations on uniprocessor and ring-interconnected distributed-memory multiprocessor database machines. This paper presents several extensions to the centralized and distributed hybrid-hash algorithms. These extensions are based on the usage of one or more bit-vectors as filters. A comparative performance study to the presented algorithms is carried out. In a uniprocessor environment, this study shows that one of the proposed filter-based algorithms outperforms all of the other ones, including the hybrid-hash algorithm. In a distributed environment, the filter-based algorithms are found to suffer from a serious problem, namely, overloading the interconnection network with the transmission of large size bit-vectors. Different compression schemes are proposed to reduce the size of a transmitted bit-vector. The augmentation of the distributed version of best-performing centralized algorithm with one of the proposed compression schemes have been found to outperform all of the other algorithms and substantially improves the performance of the join operation.

Parallel processing of XML databases

Beowulf cluster is a name given to a high performance, low-cost parallel computer system made of commodity hardware and software components. It consists of a number of processing nodes, interconnected via a switch. The extensible markup language (XML) data model, on the other hand, has recently gained huge popularity because of its ability to represent a wide variety of structured (tabular-like) and semi-structured (textual-like) data. Several query languages have been proposed for the XML data model, the most-widely known is XQuery. This paper reviews the XML data model and its query language within the context of cluster/parallel computing environment. It examines several techniques for structuring and storing XML data across the different cluster nodes. It develops a number of algorithms suitable for processing a certain class of queries, namely, the containment queries, against the parallel XML database. This paper also shows that one of these algorithms, the one that takes advantage of the parallelism existing between the different documents within the XML database, is outperforming all of the other presented ones

The strong partial transitive-closure problem: algorithms and performance evaluation

The development of efficient algorithms to process the different forms of transitive-closure (TC) queries within the context of large database systems has recently attracted a large volume of research efforts. In this paper, we present two new algorithms suitable for processing one of these forms, the so called strong partially instantiated transitive closure, in which one of the querys arguments is instantiated to a set of constants and the processing of which yields a set of tuples that draw their values from both of the querys instantiated and uninstantiated arguments. These algorithms avoids the redundant computations and high storage cost found in a number of similar algorithms. Using simulation, this paper compares the performance of the new algorithms with those found in literature and shows clearly the superiority of the new algorithms.