Marius Feldmann

Contact graph routing in DTN space networks: overview, enhancements and performance

Delay- and Disruption Tolerant Networks (DTNs) are based on an overlay protocol and on the store-carry-forward paradigm. In practice, each DTN node can store information for a long time before forwarding it. DTNs are particularly suited to cope with the challenges imposed by the space environment. This paper is focused on routing in space DTNs, and in particular on contact graph routing (CGR) and its most representative enhancements, available in the literature, which are briefly surveyed in this work. Moreover, the applicability and the obtained performance of the DTN protocol stack and of the CGR have been evaluated by presenting results from real experimental experiences such as the Deep Impact Network experiment (employing the EPOXI space cruise), the JAXA jointly performed space link demonstrations with NASA (where the JAXAs GEO relay satellite called Data Relay Test Satellite has been used), the Space Data Routers European Project, and the pilot operation of a DTN implementation on the International Space Station (ISS).

Ad-Hoc Usage of Web Services with Dynvoker

While web services are often targeted at machine-to-machine communication, they are also increasingly used directly in the interactions between humans and machines. Instead of developing specialised client applications for the invocation of these services, a generic human-driven ad-hoc usage is beneficial in many scenarios, including rapid service testing and dynamic inclusion of services as plugins into applications. We argue for the need for such a usage and extract requirements for generic web service clients. We then present a few selected use cases and introduce the Dynvoker client which already passes the majority of evaluation criteria. With its technical capabilities and open and vivid development, we consider it the most suitable and flexible generic client available and therefore highlight its role as a central component in a user-centric web service research project.

The ServFace builder - A WYSIWYG approach for building service-based applications

In this paper we present the ServFace Builder, an authoring tool that enables people without programming skills to design and create service-based interactive applications in a graphical manner. The tool exploits the concept of service annotations for developing multipage interactive applications targeting various platforms and devices.

Overview of an end-user enabled model-driven development approach for interactive applications based on annotated services

Developing Service-based interactive applications is a time consuming and nontrivial task. The idea of annotating Web Services with information fragments used for deriving parts of interactive applications automatically promises the simplification of this task, thus enabling the creation of Service-based interactive applications for end-users without any implementation skills. The paper discusses a model-driven approach for generating executable Service-based interactive applications directly from the output of a visual authoring tool. Besides the introduction of details about the model-driven methodology, this paper makes two central contributions: Firstly, technical details about the developed end-user enabled authoring tool are introduced. Secondly, the meta-model applied as serialization format of the authoring tool and as input for an application generation approach is presented.

An Integrated Approach for Creating Service-Based Interactive Applications

While the implementation of business logic and business processes based on service-oriented architectures is well-understood and covered by existing development approaches, integrated concepts that empower users to exploit the Internet of Services to create complex interactive applications are missing. In this paper, we present an integrated approach that fills this gap. Our approach builds upon service annotations that add meta-information related to user interface generation, service dependencies, and service composition to existing service descriptions. Services can be composed visually to complex interactive applications based on these annotations without the need to write any code. The application code is generated completely from the service composition description. Our approach is able to support heterogeneous target environments ranging from client/server architectures to mobile platforms.

Entity Extraction from the Web with WebKnox

This paper describes a system for entity extraction from the web. The system uses three different extraction techniques which are tightly coupled with mechanisms for retrieving entity rich web pages. The main contributions of this paper are a new entity retrieval approach, a comparison of different extraction techniques and a more precise entity extraction algorithm. The presented approach allows to extract domain-independent information from the web requiring only minimal human effort.

Assessing Contact Graph Routing Performance and Reliability in Distributed Satellite Constellations

Existing Internet protocols assume persistent end-to-end connectivity, which cannot be guaranteed in disruptive and high-latency space environments. To operate over these challenging networks, a store-carry-and-forward communication architecture called Delay/Disruption Tolerant Networking (DTN) has been proposed. This work provides the first examination of the performance and robustness of Contact Graph Routing (CGR) algorithm, the state-of-the-art routing scheme for space-based DTNs. To this end, after a thorough description of CGR, two appealing satellite constellations are proposed and evaluated by means of simulations. Indeed, the DtnSim simulator is introduced as another relevant contribution of this work. Results enabled the authors to identify existing CGR weaknesses and enhancement opportunities.

Refining the ring road-delays and path lengths in a LEO satellite message-ferry network

The so-called Ring Road approach leverages low-cost LEO satellites and delay-tolerant networking (DTN) technologies to transfer data between different ground stations and, thus, renders cost-efficient worldwide communication possible. Applying DTN protocols to LEO satellite networks is a perfect fit. Nevertheless, there are central gaps in the state of the art in the context of this type of infrastructure: Firstly, no precise systematic description of Ring Road networks is available. Secondly, to this date no detailed analysis on the specific delays and end-to-end path lengths of these networks has been conducted. Thus, the discussion about the Ring Road concept and technical solutions for realizing such networks stays very general. In this paper we close both gaps. In addition to providing a more detailed description and a classification of Ring Road networks, we present an investigation of the delay and path length characteristics based on realistic satellite trajectories. The results are intended not only to further systematize research on Ring Road networks but also to establish an argumentative basis for developing dedicated routing protocols optimized for this domain.

μPCN — A bundle protocol implementation for microcontrollers

Over the last decade, Delay-Tolerant Networking (DTN) has evolved from a new idea to a set of ready-to-use specifications and implementations. Substantial research and development efforts have been devoted to enabling new forms of communication via these solutions in contexts not addressed by earlier communication approaches. A few years ago, the Ring Road concept has been proposed as a potential usage field of DTN protocols. Its core idea is to leverage low-cost satellites (e.g. CubeSats) to enable world-wide communication and access to the Internet for low investment costs. Though many DTN protocol implementations are available, there is none that fully fits this application domain in the case a microcontroller with restricted memory and processing resources is used. In this paper a novel DTN protocol implementation named Micro Planetary Communication Network is introduced. It is intended for microcontroller platforms and offers a new routing approach designed for the application in a Ring Road infrastructure.

System Architecture for Handling the Information Overload in Enterprise Information Aggregation Systems

Nowadays, many information workers are experiencing a serious problem: too many information sources have to be tracked and monitored for important information leading to information overload. State-of-the-art information aggregation systems have not solved this problem yet. In this paper a novel system architecture is proposed which can be applied in highly scalable information aggregation systems solving this problem. Such a system can be used to aggregate heterogeneous information sources and present the results to a user in a personalized manner. The architecture is derived from a specific information processing model described in this paper. The validity of the system architecture has been confirmed by a web-based information aggregation system realized based on this architecture. The implementation is supposed to be a framework for various novel information extraction and relation detection algorithms discussed in follow-up publications.