Scalable Data Integration for Linked Data

Linked Data describes an extensive set of structured but heterogeneous datasources where entities are connected by formal semantic descriptions. In thevision of the Semantic Web, these semantic links are extended towards theWorld Wide Web to provide as much machine-readable data as possible forsearch queries. The resulting connections allow an automatic evaluation to findnew insights into the data. Identifying these semantic connections betweentwo data sources with automatic approaches is called link discovery. We derivecommon requirements and a generic link discovery workflow based on similaritiesbetween entity properties and associated properties of ontology concepts. Mostof the existing link discovery approaches disregard the fact that in times ofBig Data, an increasing volume of data sources poses new demands on linkdiscovery. In particular, the problem of complex and time-consuming linkdetermination escalates with an increasing number of intersecting data sources.To overcome the restriction of pairwise linking of entities, holistic clusteringapproaches are needed to link equivalent entities of multiple data sources toconstruct integrated knowledge bases. In this context, the focus on efficiencyand scalability is essential. For example, reusing existing links or backgroundinformation can help to avoid redundant calculations. However, when dealingwith multiple data sources, additional data quality problems must also be dealtwith. This dissertation addresses these comprehensive challenges by designingholistic linking and clustering approaches that enable reuse of existing links.Unlike previous systems, we execute the complete data integration workflowvia a distributed processing system. At first, the LinkLion portal will beintroduced to provide existing links for new applications. These links act asa basis for a physical data integration process to create a unified representationfor equivalent entities from many data sources. We then propose a holisticclustering approach to form consolidated clusters for same real-world entitiesfrom many different sources. At the same time, we exploit the semantic typeof entities to improve the quality of the result. The process identifies errorsin existing links and can find numerous additional links. Additionally, theentity clustering has to react to the high dynamics of the data. In particular,this requires scalable approaches for continuously growing data sources withmany entities as well as additional new sources. Previous entity clusteringapproaches are mostly static, focusing on the one-time linking and clustering ofentities from few sources. Therefore, we propose and evaluate new approaches for incremental entity clustering that supports the continuous addition of newentities and data sources. To cope with the ever-increasing number of LinkedData sources, efficient and scalable methods based on distributed processingsystems are required. Thus we propose distributed holistic approaches to linkmany data sources based on a clustering of entities that represent the samereal-world object. The implementation is realized on Apache Flink. In contrastto previous approaches, we utilize efficiency-enhancing optimizations for bothdistributed static and dynamic clustering. An extensive comparative evaluationof the proposed approaches with various distributed clustering strategies showshigh effectiveness for datasets from multiple domains as well as scalability on amulti-machine Apache Flink cluster

SPSS Modeler Integration mit IBM DB2 Analytics Accelerator

Die vorliegende Arbeit beschreibt einen Architekturansatz, der im Rahmen einer Machbarkeitsstudie bei IBM entwickelt wurde. Dadurch wird der IBM DB2 Analytics Accelerator als eine Data-Warehouse-Appliance dazu in die Lage versetzt, über angepasste Schnittstellen Data-Mining-Modelle über entsprechende Algorithmen direkt auf dem Accelerator zu erstellen. Neben dieser Beschreibung wird die bisherige Verwendung des DB2 Analytics Accelerators sowie das zugehörige Umfeld von Datenbanksystemen bis zum System z Mainframe vorgestellt. Darauf aufbauend werden praxisnahe Anwendungsfälle präsentiert, die unter Anwendung von intelligenten Methoden auf gespeicherten Kundendaten statistische Modelle erstellen. Für diesen Prozess wird die Datengrundlage zuerst vorbereitet und angepasst, um sie dann in dem zentralen Data-Mining-Schritt nach neuen Zusammenhängen zu durchsuchen

Untersuchung von MAC-Implementationen

Benutzerbestimmte Zugriffskontrolle ist an vielen Stellen schwer zu beschränken und zu administrieren. Der Ansatz der systembestimmten Zugriffskontrolle - Mandatory Access Control - gibt die Verantwortung an das System ab und gibt Benutzern deutlich weniger Rechte. Diese Arbeit vergleicht zwei Vertreter, welche Mandatory Access Control umsetzen, einerseits das Linux Security Module Framework und andererseits das FreeBSD MAC Framework, zudem werden die wichtigsten Policy Vertreter angegeben. Auf beiden Seiten finden sich ähnliche Ansätze wie die Umsetzung als Kernelmodul und vor allem generische Fähigkeiten, allerdings sind die implementierten Funktionalitäten unter FreeBSD im Detail oft besser durchdacht oder auch ausgereifter

Fern and bryophyte endozoochory by slugs

Endozoochory plays a prominent role for the dispersal of seed plants, and dispersal vectors are well known. However, for taxa such as ferns and bryophytes, endozoochory has only been suggested anecdotally but never tested in controlled experiments. We fed fertile leaflets of three ferns and capsules of four bryophyte species to three slug species. We found that, overall, spores germinated from slug feces in 57.3% of all 89 fern and in 51.3% of all 117 bryophyte samples, showing that the spores survived gut passage of slugs. Moreover, the number of samples within which spores successfully germinated did not differ among plant species but varied strongly among slug species. This opens new ecological perspectives suggesting that fern and bryophyte endozoochory by gastropods is a so-far-overlooked mode of dispersal, which might increase local population sizes of these taxa by spore deposition on suitable substrate

Heterostructures of skutterudites and germanium antimony tellurides – structure analysis and thermoelectric properties of bulk samples

Heterostructures of germanium antimony tellurides with skutterudite-type precipitates are promising thermoelectric materials due to low thermal conductivity and multiple ways of tuning their electronic transport properties. Materials with the nominal composition [CoSb2(GeTe)_(0.5)]_x(GeTe)_(10.5)Sb_2Te_3 (x = 0–2) contain nano- to microscale precipitates of skutterudite-type phases which are homogeneously distributed. Powder X-ray diffraction reveals that phase transitions of the germanium antimony telluride matrix depend on its GeTe content. These are typical for this class of materials; however, the phase transition temperatures are influenced by heterostructuring in a beneficial way, yielding a larger existence range of the intrinsically nanostructured pseudocubic structure of the matrix. Using microfocused synchrotron radiation in combination with crystallite pre-selection by means of electron microscopy, single crystals of the matrix as well as of the precipitates were examined. They show nano-domain twinning of the telluride matrix and a pronounced structure distortion in the precipitates caused by GeTe substitution. Thermoelectric figures of merit of 1.4 ± 0.3 at 450 °C are observed. In certain temperature ranges, heterostructuring involves an improvement of up to 30% compared to the homogeneous material

Nanostructures in Te/Sb/Ge/Ag (TAGS) Thermoelectric Materials Induced by Phase Transitions Associated with Vacancy Ordering

Te/Sb/Ge/Ag (TAGS) materials with rather high concentrations of cation vacancies exhibit improved thermoelectric properties as compared to corresponding conventional TAGS (with constant Ag/Sb ratio of 1) due to a significant reduction of the lattice thermal conductivity. There are different vacancy ordering possibilities depending on the vacancy concentration and the history of heat treatment of the samples. In contrast to the average α-GeTe-type structure of TAGS materials with cation vacancy concentrations <3%, quenched compounds like Ge_(0.53)Ag_(0.13)Sb_(0.27)□_(0.07)Te_1 and Ge_(0.61)Ag_(0.11)Sb_(0.22)□_(0.06)Te_1 exhibit “parquet-like” multidomain nanostructures with finite intersecting vacancy layers. These are perpendicular to the pseudocubic 111 directions but not equidistantly spaced, comparable to the nanostructures of compounds (GeTe)_nSb_2Te_3. Upon heating, the nanostructures transform into long-periodically ordered trigonal phases with parallel van der Waals gaps. These phases are slightly affected by stacking disorder but distinctly different from the α-GeTe-type structure reported for conventional TAGS materials. Deviations from this structure type are evident only from HRTEM images along certain directions or very weak intensities in diffraction patterns. At temperatures above 400 °C, a rock-salt-type high-temperature phase with statistically disordered cation vacancies is formed. Upon cooling, the long-periodically trigonal phases are reformed at the same temperature. Quenched nanostructured Ge_(0.53)Ag_(0.13)Sb_(0.27)□_(0.07)Te_1 and Ge_(0.61)Ag_(0.11)Sb_(0.22)□_(0.06)Te_1 exhibit ZT values as high as 1.3 and 0.8, respectively, at 160 °C, which is far below the phase transition temperatures. After heat treatment, i.e., without pronounced nanostructure and when only reversible phase transitions occur, the ZT values of Ge_(0.53)Ag_(0.13)Sb_(0.27)□_(0.07)Te_1 and Ge_(0.61)Ag_(0.11)Sb_(0.22)□_(0.06)Te_1 with extended van der Waals gaps amount to 1.6 at 360 °C and 1.4 at 410 °C, respectively, which is at the top end of the range of high-performance TAGS materials

Atypical/Nor98 Scrapie Infectivity in Sheep Peripheral Tissues

Atypical/Nor98 scrapie was first identified in 1998 in Norway. It is now considered as a worldwide disease of small ruminants and currently represents a significant part of the detected transmissible spongiform encephalopathies (TSE) cases in Europe. Atypical/Nor98 scrapie cases were reported in ARR/ARR sheep, which are highly resistant to BSE and other small ruminants TSE agents. The biology and pathogenesis of the Atypical/Nor98 scrapie agent in its natural host is still poorly understood. However, based on the absence of detectable abnormal PrP in peripheral tissues of affected individuals, human and animal exposure risk to this specific TSE agent has been considered low. In this study we demonstrate that infectivity can accumulate, even if no abnormal PrP is detectable, in lymphoid tissues, nerves, and muscles from natural and/or experimental Atypical/Nor98 scrapie cases. Evidence is provided that, in comparison to other TSE agents, samples containing Atypical/Nor98 scrapie infectivity could remain PrPSc negative. This feature will impact detection of Atypical/Nor98 scrapie cases in the field, and highlights the need to review current evaluations of the disease prevalence and potential transmissibility. Finally, an estimate is made of the infectivity loads accumulating in peripheral tissues in both Atypical/Nor98 and classical scrapie cases that currently enter the food chain. The results obtained indicate that dietary exposure risk to small ruminants TSE agents may be higher than commonly believed

Untersuchung von MAC-Implementationen

Benutzerbestimmte Zugriffskontrolle ist an vielen Stellen schwer zu beschränken und zu administrieren. Der Ansatz der systembestimmten Zugriffskontrolle - Mandatory Access Control - gibt die Verantwortung an das System ab und gibt Benutzern deutlich weniger Rechte. Diese Arbeit vergleicht zwei Vertreter, welche Mandatory Access Control umsetzen, einerseits das Linux Security Module Framework und andererseits das FreeBSD MAC Framework, zudem werden die wichtigsten Policy Vertreter angegeben. Auf beiden Seiten finden sich ähnliche Ansätze wie die Umsetzung als Kernelmodul und vor allem generische Fähigkeiten, allerdings sind die implementierten Funktionalitäten unter FreeBSD im Detail oft besser durchdacht oder auch ausgereifter

Untersuchung von MAC-Implementationen

Benutzerbestimmte Zugriffskontrolle ist an vielen Stellen schwer zu beschränken und zu administrieren. Der Ansatz der systembestimmten Zugriffskontrolle - Mandatory Access Control - gibt die Verantwortung an das System ab und gibt Benutzern deutlich weniger Rechte. Diese Arbeit vergleicht zwei Vertreter, welche Mandatory Access Control umsetzen, einerseits das Linux Security Module Framework und andererseits das FreeBSD MAC Framework, zudem werden die wichtigsten Policy Vertreter angegeben. Auf beiden Seiten finden sich ähnliche Ansätze wie die Umsetzung als Kernelmodul und vor allem generische Fähigkeiten, allerdings sind die implementierten Funktionalitäten unter FreeBSD im Detail oft besser durchdacht oder auch ausgereifter