Papers by Hicham G Elmongui
Rank-aware query processing has emerged as a key requirement in modern applications. In these app... more Rank-aware query processing has emerged as a key requirement in modern applications. In these applications, efficient and adaptive evaluation of top-k queries is an integral part of the application semantics. In this article, we introduce a rank-aware query optimization framework that fully integrates rank-join operators into relational query engines. The framework is based on extending the System R dynamic programming algorithm in both enumeration and pruning. We define ranking as an interesting physical property that triggers the generation of rank-aware query plans. Unlike traditional join operators, optimizing for rank-join operators depends on estimating the input cardinality of these operators. We introduce a probabilistic model for estimating the input cardinality, and hence the cost of a rank-join operator. To our knowledge, this is the first effort in estimating the needed input size for optimal rank aggregation algorithms. Costing ranking plans is key to the full integration of rank-join operators in real-world query processing engines.
Context is any information used to characterize the situation of an entity. Examples of contexts ... more Context is any information used to characterize the situation of an entity. Examples of contexts include time, location, identity, and activity of a user. This paper proposes a general context-aware DBMS, named Chameleon, that will eliminate the need for having specialized database engines, e.g., spatial DBMS, temporal DBMS, and Hippocratic DBMS, since space, time, and identity can be treated as contexts in the general context-aware DBMS. In Chameleon, we can combine multiple contexts into more complex ones using the proposed context composition, e.g., a Hippocratic DBMS that also provides spatio-temporal and location contextual services. As a proof of concept, we construct two case studies using the same context-aware DBMS platform within Chameleon. One treats identity as a context to realize a privacy-aware (Hippocratic) database server, while the other treats space as a context to realize a spatial database server using the same proposed constructs and interfaces of Chameleon.
Location-detection devices are used ubiquitously in moving objects due to the everyday decreasing... more Location-detection devices are used ubiquitously in moving objects due to the everyday decreasing cost and simplified technology. Usually, these devices will send the moving objects' location information to a spatio-temporal data stream management system that will be then responsible for answering spatio-temporal queries related to these moving objects. Most of the existing work focused on the continuous spatio-temporal query execution. However, several outstanding challenges have been either addressed partially or not at all in the existing literature. In this paper, we focus on the optimization of multi-predicate spatio-temporal queries on moving objects. In particular, we provide a costing mechanism for continuous spatio-temporal queries. We provide for the optimization of the parameters of the spatiotemporal operators. Finally, we propose the adaptive execution of the continuous queries for spatio-temporal data stream management systems.
Materialized views can speed up query processing greatly but they have to be kept up to date to b... more Materialized views can speed up query processing greatly but they have to be kept up to date to be useful. Today, database systems typically maintain views eagerly in the same transaction as the base table updates. This has the effect that updates pay for view maintenance while beneficiaries (queries) get a free ride! View maintenance overhead can be significant and it seems unfair to have updates bear the cost.
Nowadays, RFID applications have attracted a great deal of interest due to their increasing adopt... more Nowadays, RFID applications have attracted a great deal of interest due to their increasing adoptions in supply chain management, logistics and security. They have posed many new challenges to existing underlying database technologies, such as the requirements of supporting big volume data, preserving data transition path and handling new types of queries. In this paper, we propose an efficient method to manage RFID data. We explore and take advantage of the containment relationships in the relational tables in order to support special queries in the RFID applications. The experimental evaluation conducted on an existing RDBMS demonstrates the efficiency of our method.
In this paper, we introduce PLACE*, a distributed spatio-temporal data stream management system f... more In this paper, we introduce PLACE*, a distributed spatio-temporal data stream management system for moving objects. PLACE* supports continuous spatio-temporal queries that hop among a network of regional servers. To minimize the execution cost, a new Query-Track-Participate (QTP) query processing model is proposed inside PLACE*. In the QTP model, a query is continuously answered by a querying server, a tracking server, and a set of participating servers. In this paper, we focus on query plan generation, execution and update algorithms for continuous range queries in PLACE* using QTP. An extensive experimental study demonstrates the effectiveness of the proposed algorithms in PLACE*.
Simplified technology and low costs have spurred the use of location-detection devices in moving ... more Simplified technology and low costs have spurred the use of location-detection devices in moving objects. Usually, these devices will send the moving objects' location information to a spatio-temporal data stream management system, which will be then responsible for answering spatio-temporal queries related to these moving objects. A large spectrum of research have been devoted to continuous spatio-temporal query processing. However, we argue that several outstanding challenges have been either addressed partially or not at all in the existing literature. In particular, in this paper, we focus on the optimization of multi-predicate spatio-temporal queries on moving objects. We present several major challenges related to the lack of spatio-temporal pipelined operators, and the impact of time, space, and their combination on the query plan optimality under different circumstances of query and object distributions. We show that building an adaptive query optimization framework is key in addressing these challenges and coping with the dynamic nature of the environment we are evolving in.
This paper presents a framework for building and continuously maintaining spatio-temporal histogr... more This paper presents a framework for building and continuously maintaining spatio-temporal histograms (ST-Histograms, for short). ST-Histograms are used for selectivity estimation of continuous pipelined query operators. Unlike traditional histograms that examine and/or sample all incoming data tuples, ST-Histograms are built by monitoring the actual selectivities of the outstanding continuous queries. ST-Histograms have three main features: (1) The ST-Histograms are built with (almost) no overhead to the system. We use only feedback (i.e., the actual selectivity) from the existing continuous queries. (2) Rather than wasting system resources in maintaining accurate histograms for the whole spatial space, we only maintain accurate histograms for that part of the space that is relevant to the current existing queries. The rest of the space has less accurate histograms. The ST-Histograms are equipped with a periodicity detection procedure that predicts the future execution of the continuous queries. Hence, the query processing engine can continuously adapt the continuous query pipeline to reflect this prediction. Experimental results based on a real implementation inside a data stream management system show a superior performance of ST-Histograms in terms of providing accurate operator selectivity estimations with no extra overhead.
tance, yet these interactions are managed inefficiently. One of the major sources of inefficiency... more tance, yet these interactions are managed inefficiently. One of the major sources of inefficiency in supply-chain management is information asymmetry; i.e., information that is available to one or more organizations in the chain (e.g., manufacturer, retailer) is not available to others. There are several causes of information asymmetry, among them fear that a powerful buyer or supplier will take advantage of private information, that information will leak to a competitor, etc. We propose Secure Supply-Chain Collaboration (SSCC) protocols that enable supply-chain partners to cooperatively achieve desired system-wide goals without revealing the private information of any of the parties, even though the jointly-computed decisions require the information of all the parties. Secure supply-chain collaboration has the potential to improve supply-chain management practice, and, by removing one major inefficiency therein, improve productivity. We present specific SSCC protocols for two types of supply-chain interactions: Capacity allocation, and e-auctions. In the course of doing so, we design techniques that are of independent interest, and are likely to be useful in the design of future SSCC protocols.
In this paper, new algorithms are presented for the calculation of gray-level distance transforms... more In this paper, new algorithms are presented for the calculation of gray-level distance transforms, in which the distance values of pixels are proportional to the grayvalue dierences of minimal paths , not the gray v alues themselves, which is the case in [1] and . The presented algorithms are sequential local transform algorithms. The performance of the algorithms are evaluated by testing how quickly they converge to the errorfree distance image. It is shown that the presented algorithms are faster than the previously presented algorithms [5] for gray-level distance transforms. It turns out that the 4-neighbor, 4-raster algorithm is the fastest, converging to a distance image with no erroneous pixels in only two iteration rounds. Furthermore, because of the raster scanning approach they are easily applied other image grids than the rectangular one, and are easy to implement.
CREATE OBJECT CONTEXT patient_privacy_pref ( recipient varchar(30), purpose varchar(30), pid inte... more CREATE OBJECT CONTEXT patient_privacy_pref ( recipient varchar(30), purpose varchar(30), pid integer, pid_pref boolean, name_pref boolean, age_pref boolean, address_pref boolean, phone_pref boolean, BINDING KEY(pid) REFERENCES patient(pid) ); CREATE OBJECT CONTEXT policy_signature ( pid integer, sign_date date, BINDING KEY(pid) REFERENCES patient(pid) ); CREATE POSITIVE CONTEXT identity_activity ( job varchar(30), activity varchar(30), BINDING KEY(job, activity) REFERENCES patient_privacy_pref(recipient, purpose) SUBSTITUTE patient(pid) WITH (CASE WHEN patient_privacy_pref.pid_pref AND today() <= policy_signature.sign_date + 90 THEN patient.pid ELSE NULL), SUBSTITUTE patient(name) WITH (CASE WHEN patient_privacy_pref.name pref AND today() <= policy_signature.sign date + 90 THEN patient.name ELSE NULL) ... ) AS EQUIVALENCE WITH UNLISTED EXCLUDED;
data types Storage engine Query processor SQL Language Continuous Window Queries Stream_Scan Oper... more data types Storage engine Query processor SQL Language Continuous Window Queries Stream_Scan Operator +/ u /-Tuples WINDOW <predicate>
Proceedings of the 35th …, Jan 1, 2009
November 2006PLACE*: A Distributed Spatio-Temporal Data Stream Management System for Moving Objects
Citeseer
Moving objects equipped with locating devices can report their locations periodically to data str... more Moving objects equipped with locating devices can report their locations periodically to data stream sewers. With the pervasiveness of moving objects, one single sewer cannot support all objects and queries in a wide area. As a result, multiple spatio-temporal data stream ...
CERIAS Tech Report 2003-13 SECURE SUPPLY-CHAIN PROTOCOLS
Citeseer
Supply chain interactions have huge economic importance, yet these interactions are managed ineff... more Supply chain interactions have huge economic importance, yet these interactions are managed inefficiently. One of the major sources of inefficiency in supply-chain management is information asymmetry; ie, information that is available to one or more organizations in the chain (eg, ...
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Papers by Hicham G Elmongui