Constant propagation versus join reordering in datalog

Constant propagation and join reordering are two standard optimization techniques used for Datalog programs. These techniques have typically been studied independently of one another. However, in order to achieve constant propagation it is sometimes necessary to impose a certain join ordering on a given program. In the worst case this ordering may result in efficiencies which overcome the benefit of constant propagation. Thus the goal of constant propagation should not necessarily be pursued to the exclusion of all else. We study this problem in the context of GraphLog, a visual language whose queries are graphical notations which are translated into Datalog. We study two translation schemes from GraphLog to Datalog, one which always achieves constant propagation and another which does not. We show that each translation can significantly outperform the other. We demonstrate this by both measuring execution times using actual application data, and by providing analytical formulae to explain the trade-off between constant propagation and join reordering

A Structured Text ADT for Object-Relational Databases

There is a growing need to develop tools that are able to retrieve relevant textual information rapidly, to present textual information in a meaningful way, and to integrate textual information with related data retrieved from other sources. These tools are critical to support applications within corporate intranets and across the rapidly evolving World Wide Web. This paper introduces a framework for modelling structured text and presents a small set of operations that may be applied against such models. Using these operations structured text may be selected, marked, fragmented, and transformed into relations for use in relational and object-oriented database systems. The extended functionality has been accepted for inclusion within the SQL/MM standard, and a prototype database engine has been implemented to support SQL with the proposed extensions. This prototype serves as a proof of concept intended to address industrial concerns, and it demonstrates the power of the proposed abstrac..

Assessment of airway hyperreactivity: comparison of forced spirometry and body plethysmography for methacholine challenge tests

<p>Abstract</p> <p>Introduction</p> <p>Bronchial challenge tests by inhalation of aerosolized methacholine (MCH) are commonly used in the clinical diagnosis of airway hyperresponsiveness (AHR). While the detection of airway narrowing relies on the patient's cooperation performing forced spirometry, body plethysmographic measurements of airway resistance are less depending on the patient's cooperation and do not alter the respiratory tract by maximal maneuvers. Hence we compared both methods concerning their clinical value and correlation during MCH challenges in patients with asthma.</p> <p>Materials and Methods</p> <p>Cumulative MCH challenges test, consisting of up to 5 steps, evaluated with body plethysmography on each step were performed in 155 patients with bronchial asthma. Airway responses were recorded at each step of MCH application (Master-Screen Body, Cardinal Health, Höchberg). At the baseline test and after crossing the provocation dose (PD) threshold in body plethysmography (PD+100 sReff), forced expirations were performed and FEV₁, FVC, and FEV₁%FVC were measured. Using regression analysis of the airway parameters and taking the MCH dose as the covariate, we could extrapolate to missing spirometric values and interpolate the estimated MCH dose when crossing the PD threshold (PD-20 FEV₁) between two consecutive measurements. The administered PD+100 MCH doses for specific airway resistance, sRtot, and sReff were compared with resistance parameters Rtot and Reff, and to PD-20 of FEV₁and FEV₁%FVC.</p> <p>Results</p> <p>Regarding sReff we found a mild, moderate, or severe AHR in 114 patients (75%), but only 50 (32%) according to FEV₁. A statistical analysis showed strongly linear correlated parameters of airway resistance, but no significant correlation between the results of body plethysmography and forced spirometry</p> <p>Conclusions</p> <p>Using MCH challenges, we found specific airway resistance to be the most sensitive parameter to detect AHR. Raw is largely independent of height and gender facilitating the interpretation of measurements carried out longitudinally.</p

Generating shifting workloads to benchmark adaptability in relational database systems

Abstract. A large body of research concerns the adaptability of database systems. Many commercial systems already contain autonomic processes that adapt configurations as well as data structures and data organization. Yet there is virtually no possibility for a just measurement of the quality of such optimizations. While standard benchmarks have been developed that simulate real-world database applications very precisely, none of them considers variations in workloads produced by human factors. Today’s benchmarks test the performance of database systems by measuring peak performance on homogeneous request streams. Nevertheless, in systems with user interaction access patterns are constantly shifting. We present a benchmark that simulates a web information system with interaction of large user groups. It is based on the analysis of a real online eLearning management system with 15,000 users. The benchmark considers the temporal dependency of user interaction. Main focus is to measure the adaptability of a database management system according to shifting workloads. We will give details on our design approach that uses sophisticated pattern analysis and data mining techniques