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An advantage of modeling data as a graph – as opposed to a relational data model – is that data graph does not require a data schema from the very beginning. Hence graph data is often loaded from external sources with ad-hoc mappings. However, a Knowledge Graph is mostly understood as a data graph enhanced with a schema, a mechanism to distinguish between data and meta-data and sometimes even axioms/rules. Schemata are of great benefit as they describe the structure and semantics of the data in the graph. KG schemata enable Different views at various levels of abstraction for a better overview, Explicit and therefore exchangeable meaning of the graph data, Higher query performance, Reasoning by means of axioms/rules. The tutorial will explain the various schema modeling options for Labeled Property as well as RDF graph data models. We describe the different ways of representing schema information in both models and whether those models are embedded in the data graph or layered above it. Furthermore, we discuss similarities and mutual correspondences as well as advantages and shortcomings of the two graph models. The tutorial will demonstrate tools for the development, maintenance and review of schemas and exemplarily show how to develop and refine KG schemata in both models. In addition, attendees will have the opportunity to work with available KGs and tools to get hands-on experience.

Grasping large Knowledge Graphs is challenging. We present SemSpect, an innovative tool that brings together overview and detail view into one perspective by visually aggregating graph nodes and relationships for efficient exploration and data-driven querying of graphs. It comes either with a reasoning back-end for OWL RL for RDF or as a brand-new Graph App for Neo4j. In our talk we will report on experiences with business-critical, real-world Knowledge Graphs from various domains such as engineering industry, life sciences and intelligence.

OA gold - CA extern Magnetic resonance imaging (MRI) at ultra-high fields (UHF), such as 7 T, provides an enhanced signal-to-noise ratio and has led to unprecedented high-resolution anatomic images and brain activation maps. Although a variety of radio frequency (RF) coil architectures have been developed for imaging at UHF conditions, they usually are specialized for small volumes of interests (VoI). So far, whole-body coil resonators are not available for commercial UHF human whole-body MRI systems. The goal of the present study was the development and validation of a transmit and receive system for large VoIs that operates at a 7 T human whole-body MRI system. A Metamaterial Ring Antenna System (MRAS) consisting of several ring antennas was developed, since it allows for the imaging of extended VoIs. Furthermore, the MRAS not only requires lower intensities of the irradiated RF energy, but also provides a more confined and focused injection of excitation energy on selected body parts. The MRAS consisted of several antennas with 50 cm inner diameter, 10 cm width and 0.5 cm depth. The position of the rings was freely adjustable. Conformal resonant right-/ left-handed metamaterial was used for each ring antenna with two quadrature feeding ports for RF power. The system was successfully implemented and demonstrated with both a silicone oil and a water-NaCl-isopropanol phantom as well as in vivo by acquiring whole-body images of a crab-eating macaque. The potential for future neuroimaging applications was demonstrated by the acquired high-resolution anatomic images of the macaque's head. Phantom and in vivo measurements of crab-eating macaques provided high-resolution images with large VoIs up to 40 cm in xy-direction and 45 cm in z-direction. The results of this work demonstrate the feasibility of the MRAS system for UHF MRI as proof of principle. The MRAS shows a substantial potential for MR imaging of larger volumes at 7 T UHF. This new technique may provide new diagnostic potential in spatially extended pathologies such as searching for spread-out tumor metastases or monitoring systemic inflammatory processes.

Nominal schemas have recently been introduced as a new approach for the integration of DL-safe rules into the Description Logic framework. The efficient processing of knowledge bases with nominal schemas remains, however, challenging. We address this by extending the well-known optimisation of absorption as well as the standard tableau calculus to directly handle the (absorbed) nominal schema axioms. We implement the resulting extension of standard tableau calculi in the novel reasoning system Konclude and present further optimisations. In our empirical evaluation, we show the effect of these optimisations and we find that the proposed nominal schema handling performs well even when compared to (hyper)tableau systems with dedicated rule support.

In their pioneering publication [1] Brunner et al. have proposed propagating traveling waves as a very efficient mean to provide uniform, circularly polarized, Radio frequency (RF) B1 fields along the bore of a high-field (7T) MRI scanner while relying on the bore’s fundamental circular waveguide mode (TE11). Most of the current traveling-wave excitation schemes rely on closed-end antenna systems, which pose a serious challenge to the patient’s comfort. As a workaround to this drawback and in support of either selectivity or uniformity in the longitudinal magnetic field profile we are investigating a fully adaptive RF antenna system that perfectly conforms to the bore surface [2-4]. Fig. 1 depicts the MetaBore [5], which labels our «open» excitation architecture consisting of multiple composite right-/left-handed (CRLH) metamaterial ring antennas, each supporting a full-wave resonance (at 298 MHz) with an azimuthal current density profile that perfectly mimics the surface current distribution of the TE11 mode with respect to the given specific bore diameter. In our present research we are now looking for most efficient (potentially real-time) solutions to then inverse problem, encompassing all quadrature current amplitudes and phases of the periodically arranged ring antennas, in order to get correspondingly tailored field profiles along the bore. Besides our extensive numerical studies we have set up an experimental system for validation purposes that is designed for an easy insertion into the scanner for first proofs of concept.

Nowadays, saturation-based reasoners for the OWL EL profile are able to handle large ontologies such as SNOMED very efficiently. However, saturation-based reasoning procedures become incomplete if the ontology is extended with axioms that use features of more expressive Description Logics, e.g., disjunctions. Tableau-based procedures, on the other hand, are not limited to a specific OWL profile, but even highly optimised reasoners might not be efficient enough to handle large ontologies such as SNOMED. In this paper, we present an approach for tightly coupling tableau- and saturation-based procedures that we implement in the OWL DL reasoner Konclude. Our detailed evaluation shows that this combination significantly improves the reasoning performance on a wide range of ontologies.

This report aims at summarizing the current activities around OWL, the Web Ontology Language. At first, the report will present details about the current effort towards a revision of the official OWL W3C recommendation, known as OWL 1.1. Secondly, it describes a selection of inference engines while discussing different approaches as well as conceptual limits. These systems are then empirically evaluated using a set of spot tests which are intentionally designed to be hard to solve but small in size. Thirdly, it discusses actual trends and forthcoming developments in the context of ontology development and ontology reasoning. As a whole this report tries to provide some insights into currently available reasoning systems in order to serve as a decision help for Semantic Web application designers.

Schutzrecht: DE 10 2011 111 996 (Anmeldung 29.08.2011) Die Antennenvorrichtung soll ein lokal angepasstes Ausleuchten des gesamten Untersuchungsvolumens eines Wanderwellen-Magnetresonanztomographen gewährleisten, dabei die hochfrequente Feldenergie in Abhängigkeit vom jeweiligen Patienten zielgerichtet auf die zu untersuchenden Körperabschnitte konzentriert wird. Durch Superposition angeregter Wellen direktional wirkende Metaleitungswechselwirkungsringe erzeugen individuell angepasste lokale magnetische Feldstärken mit Hilfe konstruktiver oder destruktiver Interferenzen im Untersuchungsvolumen. Die durch den Patienten dort modifizierten elektromagnetischen Feldverhältnisse werden dazu zuvor messtechnisch ermittelt und entsprechend ausgewertet. Die Antennenvorrichtung dient zur lokal gesteuerten und individuell angepassten Wechselwirkung mit dem hochfrequenten magnetischen Wechselfeld in modernen Hochfeld-Wanderwellen-Magnetresonanztomographen.

Poster-Abstract

In their seminal publication Brunner et al. [1]have pioneered the distribution of the RF B1-field using the propagation of traveling waves within the bore of the 7 T MRI scanner. A common feature of most traveling-wave approaches is a waveguide mode excitation that relies on a closed-end antenna system at the bore end. We therefore propose an adaptive RF antenna system for the excitation (and control) of the fundamental circular waveguide mode (TE11), consisting of multiple «flat» composite right-/left-handed (CRLH) metamaterial ring antennas [cf. Fig.1(a)]that fully conforms to the inner surface of the MRI bore [2], and therefore yields no drawbacks in terms of patient’s comfort.