Universität Rostock, Lehrstuhl Datenbank- und Informationssysteme: Dbis Repository
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Query Rewriting by Contract under Privacy Constraints
Get PDFIn this paper we show how Query Rewriting rules and Containment checks of aggregate queries can be combined with Contract-based programming techniques. Based on the combination of both worlds, we are able to find new Query Rewriting rules for queries containing aggregate constraints. These rules can either be used to improve the overall system performance or, in our use case, to implement a privacy-aware way to process queries. By integrating them in our PArADISE framework, we can now process and rewrite all types of OLAP queries, including complex aggregate functions and group-by extensions. In our framework, we use the whole network structure, from data producing sensors up to cloud computers, to automatically deploy an edge computing subnetwork. On each edge node, so-called fragment queries of a genuine query are executed to filter and to aggregate data on resource restricted sensor nodes. As a result of integrating Contract-based programming approaches, we are now able to not only process less data but also to produce less data in the result. Thus, the privacy principle of data minimization is accomplished
Vergleich zeilen- und spaltenorientierter DBMS als Basis für die Parallelisierung von Vektorraumoperationen auf einem Cluster-Rechner
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The Theory behind Minimizing Research Data -- Result equivalent CHASE-inverse Mappings
Get PDFIn research data management and other applications, the primary research data have to be archived for a longer period of time to guarantee the reproducibility of research results. How can we minimize the amount of data to be archived, especially in the case of constantly changing databases or database schemes and permanently performing new evaluations on these data? In this article, we will consider evaluation queries given in an extended relational algebra. For each of the opera- tions, we will decide whether we can compute an inverse mapping to automatically compute a (minimal) subdatabase of the original research database when only the evaluation query and the evaluation result is stored. We will distinguish between different types of inverses from ex- act inverses to data exchange equivalent inverses. If there is no inverse mapping, especially for aggregation operations, we will derive the nec- essary provenance information to be able to perform the calculation of this subdatabase. The theory behind this minimization of research data, that has to be archived to guarantee reproducible research, is based on the CHASE&BACKCHASE technique, the theory of schema mappings and their inverses, and the provenance polynomials to be used for how provenance
Combining Provenance Management and Schema Evolution
Get PDFThe combination of provenance management and schema evolution using the CHASE algorithm is the focus of our research in the area of research data management. The aim is to combine the construc- tion of a CHASE inverse mapping to calculate the minimal part of the original database — the minimal sub-database — with a CHASE-based schema mapping for schema evolution
CHASE und BACKCHASE: Entwicklung eines Universal-Werkzeugs für eine Basistechnik der Datenbankforschung
Get PDFDer CHASE-Algorithmus ist ein seit vielen Jahren in der Datenbanktheorie eingesetztes Verfahren, welches mitunter in den Bereichen der semantischen Optimierung von Anfragen, Reformulierung von An- fragen auf Sichten, Datenintegration, konzeptionellen Datenbankentwurf und Provenance-Management eingesetzt wird. Während es viele Tools gibt, die den CHASE in jeweils einem der genannten Bereiche umsetzen, existiert bislang keines, das den CHASE auf mehrere Bereiche anwendbar macht. Diese Ar- beit stellt das Gerüst eines solchen Tools vor, das die Theorie des CHASE nahezu eins-zu-eins umsetzt und diese einfach anwendbar macht. Es kann den Standard-CHASE auf eine Datenbankinstanz mit In- tegritätsbedingungen anwenden und daraus eine Instanz erstellen, die die Integritätsbedingungen erfüllt. Ausgehend davon kann das Tool als Grundlage für die Anwendung des CHASE auf die verschiedenen Szenarien dienen
