The Experts below are selected from a list of 16422 Experts worldwide ranked by ideXlab platform
Davide Martinenghi - One of the best experts on this subject based on the ideXlab platform.
-
Database Technologies: Concepts, Methodologies, Tools, and Applications - Database Integrity Checking
Database Technologies, 2009Co-Authors: Hendrik Decker, Davide MartinenghiAbstract:Integrity constraints (or simply “constraints”) are formal representations of invariant conditions for the semantic cor-rectness of Database records. Constraints can be expressed in declarative languages such as datalog, predicate logic, or SQL. This article highlights the historical background of Integrity constraints and the essential features of their simplified incremental evaluation. It concludes with an outlook on future trends.
-
checking violation tolerance of approaches to Database Integrity
Lecture Notes in Computer Science, 2006Co-Authors: Hendrik Decker, Davide MartinenghiAbstract:A hitherto unquestioned assumption made by all methods for Integrity checking has been that the Database satisfies its constraints before each update. This consistency assumption has been exploited for improving the efficiency of determining whether Integrity is satisfied or violated after the update. Based on a notion of violation tolerance, we present and discuss an abstract property which, for any given approach to Integrity checking, is an easy, sufficient condition to check whether the consistency assumption can be abandoned without sacrificing usability and efficiency of the approach. We demonstrate the usefulness of our definitions by showing that the theorem-proving approach to Database Integrity by Sadri and Kowalski, as well as several other well-known methods, can indeed afford to abandon the consistency assumption without losing their efficiency, while their applicability is vastly increased.
-
On Simplification of Database Integrity Constraints
Fundamenta Informaticae, 2006Co-Authors: Henning Christiansen, Davide MartinenghiAbstract:Without proper simplification techniques, Database Integrity checking can be prohibitively time consuming. Several methods have been developed for producing simplified incremental checks for each update but none until now of sufficient quality and generality for providing a true practical impact, and the present paper is an attempt to fill this gap. On the theoretical side, a general characterization is introduced of the problem of simplification of Integrity constraints and a natural definition is given of what it means for a simplification procedure to be ideal. We prove that ideality of simplification is strictly related to query containment; in fact, an ideal simplification pro-cedure can only exist in Database languages for which query containment is decidable. However, simplifications that do not qualify as ideal may also be relevant for practical purposes. We present a concrete approach based on transformation operators that apply to Integrity constraints written in a rich DATALOG-like language with negation. The resulting procedure produces, at design-time, simplified constraints for parametric transaction patterns, which can then be instantiated and checked for consistency at run-time. These tests take place before the execution of the update, so that only consistency-preserving updates are eventually given to the Database. The extension to more expressive languages and the application of the framework to other contexts, such as data integration and concurrent Database systems, are also discussed. Our experiments show that the simplifications obtained with our method may give rise to much better performance than with previous methods and that further improvements are achieved by checking consistency before executing the update.
-
ADVIS - Checking violation tolerance of approaches to Database Integrity
Advances in Information Systems, 2006Co-Authors: Hendrik Decker, Davide MartinenghiAbstract:A hitherto unquestioned assumption made by all methods for Integrity checking has been that the Database satisfies its constraints before each update. This consistency assumption has been exploited for improving the efficiency of determining whether Integrity is satisfied or violated after the update. Based on a notion of violation tolerance, we present and discuss an abstract property which, for any given approach to Integrity checking, is an easy, sufficient condition to check whether the consistency assumption can be abandoned without sacrificing usability and efficiency of the approach. We demonstrate the usefulness of our definitions by showing that the theorem-proving approach to Database Integrity by Sadri and Kowalski, as well as several other well-known methods, can indeed afford to abandon the consistency assumption without losing their efficiency, while their applicability is vastly increased.
-
Simplification of Database Integrity constraints revisited: A transformational approach
Lecture Notes in Computer Science, 2004Co-Authors: Henning Christiansen, Davide MartinenghiAbstract:Complete checks of Database Integrity constraints may be prohibitively time consuming, and several methods have been suggested for producing simplified checks for each update. The present approach introduces a set of transformation operators that apply to Database Integrity constraints with each operator representing a concise, semantics-preserving operation. These operators are applied in a procedure producing simplified constraints for parametric transaction patterns, which then can be instantiated and checked for consistency at run-time but before any transaction is executed. The operators provide a flexibility for other Database enhancements and the work may also be seen as more systematic and general when compared with other approaches. The framework is formulated with first-order clause logic but with the perspective of being applied with present-day Database technology.
Hendrik Decker - One of the best experts on this subject based on the ideXlab platform.
-
a measured evolution of Database Integrity
Model and Data Engineering, 2013Co-Authors: Hendrik DeckerAbstract:Inconsistency in large Database systems is commonplace and therefore must be controlled in order to not get out of hand. Consistency in Database systems is encoded by Integrity constraints. Inconsistency thus corresponds to constraint violations. Database system services need to function in spite of extant Integrity violations, but inconsistency should not increase beyond control in the course of the evolution of such systems. Evolution is effected by updates that may involve insertions and deletions of relational facts as well as schema updates. We show how to determine the causes of violations. Knowledge about such causes can be used to control inconsistency: an increase of Integrity violations by updates can be prevented, while tolerating extant inconsistencies, even if the Database schema is altered, and even if the schema is unsatisfiable.
-
MEDI - A Measured Evolution of Database Integrity
Model and Data Engineering, 2013Co-Authors: Hendrik DeckerAbstract:Inconsistency in large Database systems is commonplace and therefore must be controlled in order to not get out of hand. Consistency in Database systems is encoded by Integrity constraints. Inconsistency thus corresponds to constraint violations. Database system services need to function in spite of extant Integrity violations, but inconsistency should not increase beyond control in the course of the evolution of such systems. Evolution is effected by updates that may involve insertions and deletions of relational facts as well as schema updates. We show how to determine the causes of violations. Knowledge about such causes can be used to control inconsistency: an increase of Integrity violations by updates can be prevented, while tolerating extant inconsistencies, even if the Database schema is altered, and even if the schema is unsatisfiable.
-
SDKB - Measure-Based Inconsistency-Tolerant Maintenance of Database Integrity
Semantics in Data and Knowledge Bases, 2013Co-Authors: Hendrik DeckerAbstract:To maintain Integrity, constraint violations should be prevented or repaired. However, it may not be feasible to avoid inconsistency, or to repair all violations at once. Based on an abstract concept of violation measures, updates and repairs can be checked for keeping inconsistency bounded, such that Integrity violations are guaranteed to never get out of control. This measure-based approach goes beyond conventional methods that are not meant to be applied in the presence of inconsistency. It also generalizes recently introduced concepts of inconsistency-tolerant Integrity maintenance.
-
SUM - Managing uncertainty in Databases and scaling it up to concurrent transactions
Lecture Notes in Computer Science, 2012Co-Authors: Alfredo Cuzzocrea, Hendrik Decker, Rubén De Juan Marín, Francesc D. Muñoz-escoíAbstract:Uncertainty and data Integrity are closely related. The uncertainty of data can be modeled and maintained by existing Database Integrity technology. The usual requirement that Integrity constraints must always be satisfied needs to be renounced for constraints that model uncertainty. That is possible due to the recently introduced inconsistency tolerance of methods for Integrity checking, Integrity repair and query answering. Inconsistency tolerance also enables the scaling up of uncertainty management to concurrent transactions.
-
measure based inconsistency tolerant maintenance of Database Integrity
Semantics in Data and Knowledge Bases, 2011Co-Authors: Hendrik DeckerAbstract:To maintain Integrity, constraint violations should be prevented or repaired. However, it may not be feasible to avoid inconsistency, or to repair all violations at once. Based on an abstract concept of violation measures, updates and repairs can be checked for keeping inconsistency bounded, such that Integrity violations are guaranteed to never get out of control. This measure-based approach goes beyond conventional methods that are not meant to be applied in the presence of inconsistency. It also generalizes recently introduced concepts of inconsistency-tolerant Integrity maintenance.
Steven D. Young - One of the best experts on this subject based on the ideXlab platform.
-
Database Integrity Monitoring for Synthetic Vision Systems Using Machine Vision and SHADE
Enhanced and Synthetic Vision 2005, 2005Co-Authors: Eric G. Cooper, Steven D. YoungAbstract:In an effort to increase situational awareness, the aviation industry is investigating technologies that allow pilots to visualize what is outside of the aircraft during periods of low-visibility. One of these technologies, referred to as Synthetic Vision Systems (SVS), provides the pilot with real-time computer-generated images of obstacles, terrain features, runways, and other aircraft regardless of weather conditions. To help ensure the Integrity of such systems, methods of verifying the accuracy of synthetically-derived display elements using onboard remote sensing technologies are under investigation. One such method is based on a shadow detection and extraction (SHADE) algorithm that transforms computer-generated digital elevation data into a reference domain that enables direct comparison with radar measurements. This paper describes machine vision techniques for making this comparison and discusses preliminary results from application to actual flight data.
-
Terrain Database Integrity monitoring for synthetic vision systems
IEEE Transactions on Aerospace and Electronic Systems, 2005Co-Authors: Maarten Uijt de Haag, Jacob L. Campbell, Jonathon S. Sayre, Steven D. Young, Robert A. GrayAbstract:A real-time terrain Database Integrity monitor for synthetic vision systems (SVS) that are to be used in civil aviation is presented. SVS provides pilots with advanced display technology including terrain information as well as other information about the external environment such as obstacles and traffic. The use of SVS to support strategic and tactical decision-making and the compelling nature of the terrain depiction may require terrain Database server certification at the essential and flight-critical levels. SVS and terrain Database characteristics are discussed and a failure model is identified. Real-time Integrity monitors are proposed that check the consistency between terrain profiles described by the Database and terrain profiles that are sensed in flight by either a downward-looking (DWL) sensor or a forward-looking (FWL) season A DWL sensor scheme is discussed in detail and it is shown that this scheme can provide the necessary Integrity required for an essential certification of a terrain Database server.
-
The application of LiDAR to synthetic vision system Integrity
Digital Avionics Systems Conference, 2003. DASC '03. The 22nd, 2003Co-Authors: Jacob L. Campbell, Agasteswar Vadlamani, Maarten Uijt De Haag, Steven D. YoungAbstract:One goal in the development of a Synthetic Vision System (SVS) is to create a system that can be certified by the Federal Aviation Administration (FAA) for use at various flight criticality levels. As part of NASA's Aviation Safety Program, Ohio University and NASA Langley have been involved in the research and development of real-time terrain Database Integrity monitors for SVS. Integrity monitors based on a consistency check with onboard sensors may be required if the inherent terrain Database Integrity is not sufficient for a particular operation. Sensors such as the radar altimeter and weather radar, which are available on most commercial aircraft, are currently being investigated for use in a real-time terrain Database Integrity monitor. This paper introduces the concept of using a Light Detection And Ranging (LiDAR) sensor as part of a real-time terrain Database Integrity monitor. A LiDAR system consists of a scanning laser ranger, an inertial measurement unit (IMU), and a Global Positioning System (GPS) receiver. Information from these three sensors can be combined to generate synthesized terrain models (profiles), which can then be compared to the stores SVS terrain model. This paper discusses an initial performance evaluation of the LiDAR-based terrain Database Integrity monitor using LiDAR data collected over Reno, Nevada. The paper will address the consistency checking mechanism and test statistic, sensitivity to position errors, and a comparison of the LiDAR-based Integrity monitor to a radar altimeter-based Integrity monitor.
-
Monitoring terrain Database Integrity through aircraft sensor consistency checking: architecture and flight test results
2003 IEEE International Workshop on Computer Architectures for Machine Perception, 1Co-Authors: M.u. De Haag, Jonathon Sayre, Jacob Campbell, Steven D. YoungAbstract:This paper discusses the architecture and flight test results of a digital elevation model (DEM) Integrity monitor for a synthetic vision system (SVS). An SVS provides pilots with either a heads down display (HDD) or a heads up display (HUD) containing aircraft state, guidance and navigation information, and a virtual depiction of the terrain as viewed "from the cockpit". Introduction of SVS technology in the aircraft flight deck has the potential to improve flight safety by increasing the situational awareness (SA) in low to near zero-visibility conditions to a level of awareness similar to daytime clear weather flying. This SA improvement does not only enable low-visibility operations, but may also reduce the likelihood of controlled flight into terrain (CFIT)
Andrei Voronkov - One of the best experts on this subject based on the ideXlab platform.
-
unidoor a deductive object oriented Database management system
International Conference on Data Engineering, 2006Co-Authors: M K Jaber, Andrei VoronkovAbstract:In this paper, we present UNIDOOR, a deductive objectoriented Database system (DOOD). We demonstrate the distinctive features of UNIDOOR data model and its query language. We then show how essential object-oriented and Database management features, that were missing from other DOOD implementations, are successfully supported in UNIDOOR. These features include a scalable persistent store with crash recovery, Database Integrity and transaction control facilities in a multi-user environment.
-
ICDE - UNIDOOR: a Deductive Object-Oriented Database Management System
22nd International Conference on Data Engineering (ICDE'06), 2006Co-Authors: M K Jaber, Andrei VoronkovAbstract:In this paper, we present UNIDOOR, a deductive objectoriented Database system (DOOD). We demonstrate the distinctive features of UNIDOOR data model and its query language. We then show how essential object-oriented and Database management features, that were missing from other DOOD implementations, are successfully supported in UNIDOOR. These features include a scalable persistent store with crash recovery, Database Integrity and transaction control facilities in a multi-user environment.
Maarten Uijt De Haag - One of the best experts on this subject based on the ideXlab platform.
-
Use of X-band weather radar to support the terrain Database Integrity monitoring and terrain referenced navigation function
Enhanced and Synthetic Vision 2007, 2007Co-Authors: Abhijeet Singh, Maarten Uijt De HaagAbstract:To enable safe use of Synthetic Vision Systems (SVS) at lower altitudes, real-time sensor measurements are required to ensure the Integrity of terrain and obstacle models stored in the onboard SVS and to detect hazards that may have been omitted from the stored models. This paper discusses various aspects of using X-band weather radar for terrain Database Integrity monitoring and terrain referenced navigation. Feature extraction methods will be addressed to support the correlation process between the weather radar measurements and the stored terrain Databases. Furthermore, improved weather radar antenna models will be discussed to more reliably perform the shadow detection and extraction (SHADE) functionality. In support of the navigation function, methods will be introduced to estimate aircraft state information, such as velocity, from the geometrical changes in the observed terrain imagery. The outputs of these methods will be compared to the state estimates derived from Global Positioning System (GPS) and Inertial Navigation System (INS) measurements. All methods discussed in this paper will be evaluated using flight test data collected with a Gulfstream V in Reno, NV.
-
The application of LiDAR to synthetic vision system Integrity
Digital Avionics Systems Conference, 2003. DASC '03. The 22nd, 2003Co-Authors: Jacob L. Campbell, Agasteswar Vadlamani, Maarten Uijt De Haag, Steven D. YoungAbstract:One goal in the development of a Synthetic Vision System (SVS) is to create a system that can be certified by the Federal Aviation Administration (FAA) for use at various flight criticality levels. As part of NASA's Aviation Safety Program, Ohio University and NASA Langley have been involved in the research and development of real-time terrain Database Integrity monitors for SVS. Integrity monitors based on a consistency check with onboard sensors may be required if the inherent terrain Database Integrity is not sufficient for a particular operation. Sensors such as the radar altimeter and weather radar, which are available on most commercial aircraft, are currently being investigated for use in a real-time terrain Database Integrity monitor. This paper introduces the concept of using a Light Detection And Ranging (LiDAR) sensor as part of a real-time terrain Database Integrity monitor. A LiDAR system consists of a scanning laser ranger, an inertial measurement unit (IMU), and a Global Positioning System (GPS) receiver. Information from these three sensors can be combined to generate synthesized terrain models (profiles), which can then be compared to the stores SVS terrain model. This paper discusses an initial performance evaluation of the LiDAR-based terrain Database Integrity monitor using LiDAR data collected over Reno, Nevada. The paper will address the consistency checking mechanism and test statistic, sensitivity to position errors, and a comparison of the LiDAR-based Integrity monitor to a radar altimeter-based Integrity monitor.
-
Improving the detection capability of spatial failure modes using downward-looking sensors in terrain Database Integrity monitors
Digital Avionics Systems Conference, 2003. DASC '03. The 22nd, 2003Co-Authors: Agasteswar Vadlamani, Maarten Uijt De HaagAbstract:This article discusses various methods of improving the detection capability of horizontal and vertical failure modes for a terrain Database Integrity monitor that is purely based on the inputs from downward looking sensors. Terrain Database Integrity monitors which use radar altimeter and GPS inputs have previously been proposed for Synthetic Vision Systems (SVS). An SVS provides pilots with either a Heads Down Display (HDD) or a Heads Up Display (HUD) containing aircraft state, guidance and navigation information, and a virtual depiction of the terrain as viewed "from the cockpit." The source used to generate the terrain depicted on these displays is a Digital Elevation Model (DEM). Due to the compelling nature of the displays, it is quite possible for the pilots to use the display for functions other than its original intended function. It may be hard to avoid such a scenario, especially if the system is certified as an advisory system. When using SVS display technology for functions other than advisory it may be necessary to include a DEM Integrity monitor whose performance is specified by probabilities of Missed Detection, Fault-Free Detection and Time-to-Alarm. Ideally, the DEM represents the height or elevation of the terrain at corresponding coordinates (e.g. latitude and longitude) expressed in a predefined vertical datum. However, the given elevations deviate from the true elevations due to systematic and blunder errors that are present in the DEM primarily due to the way in which they are generated from different sensor technologies such as photogrammetry, remote sensing, etc. and the manual post-processing process. Another source of error of lesser significance is the flat earth approximation over relatively larger areas, while collecting the data. The described Integrity monitor method is based on the compa
-
A terrain Database Integrity monitor for synthetic vision systems
19th DASC. 19th Digital Avionics Systems Conference. Proceedings (Cat. No.00CH37126), 2000Co-Authors: Maarten Uijt De Haag, Jacob L. Campbell, Robert A. GrayAbstract:This paper discusses a terrain Database Integrity monitor for Synthetic Vision Systems (SVS) in Civil Aviation applications. SVS provide the pilots with advanced display technology containing terrain information as well as other information about the external environment such as obstacles and traffic. SVS will improve situational awareness and thereby reduce the likelihood of Controlled Flight Into Terrain (CFIT). Safe utilization of the SVS for strategic and tactical applications may require a terrain Database Integrity check. The discussed Integrity monitor checks the consistency between the sensed terrain profile as computed from DGPS and radar altimeter data and the terrain profile as given by the terrain Databases. A case study to verify the Integrity monitor's performance is presented based on data collected during flight-testing performed by NASA at Asheville, NC
