Sebastian Ebers

Efficient processing of SPARQL joins in memory by dynamically restricting triple patterns

Since there are a lot of similar or common properties between RDF and relational databases and between SPARQL and SQL, many efforts focus on leveraging the research results of optimizing relational query languages for optimizing SPARQL queries. However, SPARQL has its own characteristics different from SQL, which are not fully exploited by existing work. Therefore, there is still much space for research on optimizing SPARQL queries. Based on the triple nature of RDF data, we create 7 indices to retrieve RDF data quickly; based on the SPARQL-specific properties and the 7 indices, we develop a new, efficient approach to computing join by dynamically restricting triple patterns. Our experimental results show the efficiency of our approach.

Using BPEL to realize business processes for an internet of things

In the vision of an IoT, trillions of tiny devices extend the Internet to the physical world and enable novel applications that have not been possible before. Such applications emerge out of the interaction of these devices with each other and with more powerful server-class computers on the Internet. Programming such applications is challenging due to the massively distributed nature of these networks combined with the challenges of embedded programming. In addition, resource constraints, device heterogeneity, and the integration with the Internet further complicate this situation. In this paper, we present a programming-in-the-large approach for resource-constraint devices such as wireless sensor nodes. Our approach is to model such applications using the Business Process Execution Language (BPEL), which is successfully and widely used in the Internet to model complete applications and business processes. However, BPEL and its associated technologies are too resourcedemanding to be directly applied in resource-constraint environments. We therefore use the BPEL model as input to a code generation process that generates custom-tailored, lean code for different target platforms. The resulting code is fully standard-compliant and allows a seamless integration of IoT devices in enterprise IT environments. We present an exhaustive evaluation on real hardware showing the first-rate performance of the approach.

Short paper: Collaboration between VANET applications based on open standards

As of today, there is a variety of self-contained vehicular ad hoc network (VANET) applications. In many scenarios, they could complement each other if they would allow for interoperability. However, since they often use different data formats and do not share a common, machine-readable and platform-independent definition of terms and semantics, they cannot mutually understand and reuse each others data. Consequently, in this paper we propose a VANET Ontology (VO) for defining the semantics of VANET relevant terms and a common VANET Data Representation (VDR) to facilitate interoperability between arbitrary VANET applications.

Methods for Improving the Flow of Traffic

We describe a distributed and self-regulated approach for the self-organisation of a large system of many self-driven, mobile objects, i.e., cars in traffic. Based on methods for mobile ad-hoc networks using short-distance communication between vehicles, and ideas from distributed algorithms, we consider reactions to specific traffic structures (e.g., traffic jams.) Building on current models from traffic physics, we are able to develop strategies that significantly improve the flow of congested traffic. Results include fuel savings up to 40% for cars in stop-and-go traffic; we present a number of simulation results illustrating the underlying mechanisms. In addition, we discuss the organic structure of urban traffic, and hint at how self-healing methods can lead to improvements in rush-hour traffic.

A Formal Definition for Nanorobots and Nanonetworks

Nano computation and communication research examines minuscule devices like sensor nodes or robots. Over the last decade, it has attracted attention from many different perspectives, including material sciences, biomedical engineering, and algorithm design. With growing maturity and diversity, a common terminology is increasingly important.

Poster: Adapter framework for VANET simulators

To evaluate applications for Vehicular Ad-Hoc Networks (VANETs) simulations are a widely used alternative to potentially costly and complex field tests. For authentic results, simulations of realistic vehicular movement and communication environment are mandatory. Usually, a traffic simulator and a network simulator are used for the first and second requirement, respectively. Some VANET simulators combine independent simulators of both domains while others implement the necessary functionality themselves. However, due to different scopes of functionality, available protocols, etc., the choice of a VANET simulator has an impact on the result. Unfortunately, VANET applications are typically implemented based on a certain VANET simulators API. Thus, applications have to be adapted when switching between simulators. To solve this problem, we developed a framework which allows for executing VANET applications in different environments without modification. We further defined a VANET API which aims at enabling portability for VANET applications. Hence, applications can be implemented independently of the used VANET simulator and can be even run on real hardware unmodified.

API for data dissemination protocols - evaluation with AutoCast

In the past various protocols inspired by nature and biology have been proposed to disseminate or transfer data in mobile or static ad-hoc networks. Many of them are designed for usage in wireless sensor networks or vehicular ad-hoc networks. Recently, we have developed and designed a general purpose data dissemination protocol called AutoCast in this field that we evaluated in detail by simulations. When we started to use AutoCast in real applications, we found out that the description of AutoCast is incomplete, as we provided the algorithms of AutoCast in details but did neither provide nor describe a suitable Application Programming Interface (API) and AutoCast was closely coupled to the application. The focus of this article is twofold. First, we propose an appropriate API to encapsulate data dissemination protocols like AutoCast and we specify the service interface of AutoCast in detail. This API can serve as a reference model for other nature and biologically inspired data dissemination approaches and applications. Second, we evaluate two applications based on our API with AutoCast in the field of wireless sensor networks and vehicular ad-hoc networks to illustrate the usage of the API and demonstrate the flexibility of this approach.

VaSili - A simulation runtime environment for applications in Vehicular Ad-Hoc Networks

In recent years, Vehicular Ad-Hoc Networks (VANETs) have become a very active research field. Since real-world experiments might involve potentially costly and complex hardware installations, simulations are a widely used alternative. However, due to, e.g., different scopes of functionality of available VANET simulators, simulations of VANET applications yield different results when using different simulators. Thus, it would be beneficial to test a VANET application in multiple simulation environments. Unfortunately, VANET applications are typically implemented inside of a certain simulator. Hence, to switch the simulator, the source code of the application has to be adapted. To solve this problem, we developed a VANET API which defines the structure and interfaces of crucial VANET components to make them accessible in a unified way. We further developed VANET Simulation Runtime (VaSili), a framework which allows executing VANET API-compliant VANET applications in different VANET simulators without modification. Hence, applications developed using our proposed API can be run in different simulation environments and, since the VANET API is independent of VaSili, on real hardware.

Hybrid underwater environmental monitoring

Many underwater monitoring tasks, such as submarine life studies and pipeline inspections, are usually performed manually. Automated underwater monitoring has the potential to increase safety, improve timeliness, and decrease costs. We propose a hybrid solution of stationary sensor buoys and swarms of autonomous underwater vehicles (AUV) and report on our current progress of its realization. Our solution is based on sensor network technology and a small mobile underwater robot developed in our institute.

BloodVoyagerS: simulation of the work environment of medical nanobots

The simulation of nanobots in their working environment is crucial to promote their application in the medical context. Several simulators for nanonetworks investigate new communication paradigms at nanoscale. However, the influence of the environment, namely the human body, on the movement and communication of nanobots was rarely considered so far. We propose a framework for simulating medical nanonetworks, which integrates a nanonetwork simulator with a body simulator. We derive requirements for a body model that forms the basis for our prototypical implementation of the body simulator BloodVoyagerS as part of the network simulator ns-3. Our evaluation shows that BloodVoyagerS successfully moves nanobots in the simulated cardiovascular system. After about 7 minutes, the nanobot distribution reaches a dynamic equilibrium. The prototype shows promise to provide a more realistic full-body simulation to investigate movement and communication of nanobots in medical applications.