Technical reports / Department Informatik
- WOM: An object model for Wikitext (2011)
- Wikipedia is a rich encyclopedia that is not only of great use to its contributors and readers but also to researchers and providers of third party software around Wikipedia. However, Wikipedia's content is only available as Wikitext, the markup language in which articles on Wikipedia are written, and whoever needs to access the content of an article has to implement their own parser or has to use one of the available parser solutions. Unfortunately, those parsers which convert Wikitext into a high-level representation like an abstract syntax tree (AST) define their own format for storing and providing access to this data structure. Further, the semantics of Wikitext are only defined implicitly in the MediaWiki software itself. This situation makes it difficult to reason about the semantic content of an article or exchange and modify articles in a standardized and machine-accessible way. To remedy this situation we propose a markup language, called XWML, in which articles can be stored and an object model, called WOM, that defines how the contents of an article can be read and modified.
- Treating Memory Management and Filesystems as One Topic (2011)
- Speicherverwaltung und Dateisysteme im Rahmen einer Betriebssysteme-Vorlesung gemeinsam zu behandeln, statt sie als separate Themen vorzustellen, kann das Verständnis der Studierenden erhöhen und auch die Klausurergebnisse verbessern. In einer Befragung äußerten sie zudem, dass ihnen diese Methode gefiel. Dieser Artikel beschreibt Veränderungen eines klassischen Betriebssysteme-Kurses und die Resultate, die sich aus dem Vergleich der Klausurergebnisse und der Umfrageauswertung ergaben.
- GPU Implementation of a Multiobjective Search Algorithm (2011)
- In this paper we observe the possibility to accelerate a search algorithm for multiobjective optimization problems with help of a graphics processing unit. Besides an implementation we present test results for it and the conclusions that can be drawn from these results.
- The Erlangen Glaucoma Registry: a Scientific Database for Longitudinal Analysis of Glaucoma (2011)
- Background: Due to the slow progression of the Glaucoma disease, a large study population and long-time observations are needed to gain insights into its long-term effects and progression rates. Since modalities can export data in machine-readable formats, statistical analyses of the large number of examinations is feasible. These data have been integrated in a central patient registry, the Erlangen Glaucoma Registry (EGR). Objectives: The primary focus of the EGR system design has been its fitness for analyses. It holds almost all the available research data for registered glaucoma patients. This allows for cross-sectional and longitudinal observations and for evaluation of prognostic validity of diagnostic procedures. Methods: An adequate technology for integration of data and flexibility in data analysis is a database management system (DBMS). Here, a careful schema design is mandatory. Adding new modalities leads to schema modifications which are supported by defining a core database schema and attaching all data to this core. On that basis, a large number of modalities have been connected to the EGR. Results: The registry contains data of 1,400 patients in the main longitudinal study. It has successfully helped in scientific research, as can be seen in a large number of published papers. For example, validation of new sensory physiological methods requires patients with reliable diagnoses. The existence of a well-documented patient collective facilitated finding such patients. Conclusions: The EGR holds a unique amount of available data gathered in large longitudinal studies. It was successful in terms of medical results obtained. Developed as an evolutionary system, it can easily be extended.
- Bitonic Sorting on Dynamically Reconfigurable Architectures (2011)
- A Computationally Inexpensive Empirical Model of IEEE 802.11p Radio Shadowing in Urban Environments (2010)
- Spezifikation und Implementation des CAN-Arbitrierungsverfahrens in UPPAAL (2010)
- In dieser Arbeit stellen wir eine durch Zeitautomaten modellierte Spezifikation des Mediumzugriffs im CAN-Protokoll vor sowie ihre Implementierung in UPPAAL. Zeitliche Anforderungen wurden dabei durch entsprechende Uhren-Nebenbedingungen erfasst. Dieses Zeitautomaten-Modell wurde anschließend automatisch verifiziert (Model Checking), wobei mehrere Anforderungen identifiziert wurden, die das CAN Protokoll erfüllen muß (wie Deadlock-Freiheit des Modells, Übertragungsrecht für die höchstpriore Nachricht, exklusives Übertragungsrecht für beliebigen CAN-Adapter nach der gewonnenen Arbitrage etc.). All diese Eigenschaften wurden in einer Variante der temporalen Logik CTL spezifiziert; die automatische Verifikation selbst wurde dabei mit UPPAAL durchgeführt, einem Model Checker für zeitautomaten-basierte Modelle.
- Irregular data-parallelism in a parallel object-oriented language by means of Collective Replication (2010)
- In parallel object-oriented languages it is hard to elegantly express efficient data-parallel operations on objects of an irregularly-shaped object structure that is spread across the parallel computing environment. This paper presents a new programming model that smoothly integrates both task and data parallelism in a distributed object-oriented context. So called Collective Replication combines enhanced data locality for parallel tasks with data-parallel computations on irregular data structures. Collectively replicated objects exploit the bulk- synchronous data-parallel pattern in an object-oriented language and relieve the programmer from explicitly coding the communication step even for irregular data structures. To make the consistency protocol efficient, only modified fields are shipped instead of whole objects. Moreover, a novel graph coloring approach is used to broadcast updates to all replicas; this technique avoids bottlenecks and is more efficient than known approaches. We suggest Java language extensions that can be han- dled by a pre-processor and achieve good performance on a set of benchmark applications.
- Improved DSM Efficiency, Flexibility, and Correctness (2010)
- A collection of research topics that together help improve distributed shared memory systems. Contents: Java/OpenMP as a language for cluster and grid computing. The Tapir language as a functional/parallel language to allow both model-checking and parallel-execution for DSM middlewares and general applications.
- Adaptive Beaconing for Delay-Sensitive and Congestion-Aware Traffic Information Systems (2010)
- We present a new car-to-X communication protocol, Adaptive Traffic Beacon (ATB), which supports the exchange of delay-sensitive traffic information in a wide range of scenarios by flexibly adapting to the availability of infrastructure elements as well as to the network load. From previous work, we see that centralized solutions and flooding based approaches each show benefits and drawbacks depending on traffic density, penetration, network utilization, and other parameters. This observation is in line with findings about intelligent transportation systems that have been developed for specific settings. In order to overcome this limitation, we designed ATB to be adaptive in two dimensions: First, the beacon interval is adapted dynamically and, secondly, the protocol can dynamically make use of available infrastructure elements. We concentrate on a Traffic Information System (TIS) with a focus on congestion-aware communication. Simulation experiments clearly demonstrate that ATB performs well in a broad range of settings. It maintains a non-congested wireless channel to prevent collisions during TIS data exchange.