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Transaction processing is of growing importance for mobile computing. Booking tickets, flight reservation, banking, ePayment, and booking holiday arrangements are just a few examples for mobile transactions. Due to temporarily disconnected situations the synchronisation and consistent transaction processing are key issues. Serializability is a too strong criteria for correctness when the semantics of a transaction is known. We introduce a transaction model that allows higher concurrency for a certain class of transactions defined by its semantic. The transaction results are ”escrow serializable” and the synchronisation mechanism is non-blocking. Experimental implementation showed higher concurrency, transaction throughput, and less resources used than common locking or optimistic protocols.
Modern web-based applications are often built as multi-tier architecture using persistence middleware. Middleware technology providers recommend the use of Optimistic Concurrency Control (OCC) mechanism to avoid the risk of blocked resources. However, most vendors of relational database management systems implement only locking schemes for concurrency control. As consequence a kind of OCC has to be implemented at client or middleware side.
A simple Row Version Verification (RVV) mechanism has been proposed to implement an OCC at client side. For performance reasons the middleware uses buffers (cache) of its own to avoid network traffic and possible disk I/O. This caching however complicates the use of RVV because the data in the middleware cache may be stale (outdated). We investigate various data access technologies, including the new Java Persistence API (JPA) and Microsoft’s LINQ technologies for their ability to use the RVV programming discipline.
The use of persistence middleware that tries to relieve the programmer from the low level transaction programming turns out to even complicate the situation in some cases.Programmed examples show how to use SQL data access patterns to solve the problem.
Die Informatics Inside-Konferenz findet in diesem Jahr zum dritten Mal statt. Mit dem Thema "Grenzen überwinden – Virtualität erweitert Realität" stellt sich die Veranstaltung einem aktuellen Schwerpunkt, der viele Interessierte aus Wirtschaft, Wissenschaft und Forschung anzieht. Die Konferenz hat sich von einer Veranstaltung für die Masterstudenten des Studiengangs Medien- und Kommunikationsinformatik zu einer offenen Studentenkonferenz entwickelt. Um die Qualität weiter zu steigern wurde parallel dazu ein zweistufiges Review-Verfahren für Beiträge dieses Tagungsbandes eingeführt.
The Third International Conference on Advances in Databases, Knowledge, and Data Applications (DBKDA 2011) held on January 23-27, 2011 in St. Maarten, The Netherlands Antilles, continued a series of international events covering a large spectrum of topics related to advances in fundamentals on databases, evolution of relation between databases and other domains, data base technologies and content processing, as well as specifics in applications domains databases. Advances in different technologies and domains related to databases triggered substantial improvements for content processing, information indexing, and data, process and knowledge mining. The push came from Web services, artificial intelligence, and agent technologies, as well as from the generalization of the XML adoption. High-speed communications and computations, large storage capacities, and load-balancing for distributed databases access allow new approaches for content processing with incomplete patterns, advanced ranking algorithms and advanced indexing methods. Evolution on e-business, ehealth and telemedicine, bioinformatics, finance and marketing, geographical positioning systems put pressure on database communities to push the ‘de facto’ methods to support new requirements in terms of scalability, privacy, performance, indexing, and heterogeneity of both content and technology. We take this opportunity to thank all the members of the DBKDA 2011 Technical Program Committee as well as the numerous reviewers. The creation of such a broad and high-quality conference program would not have been possible without their involvement. We also kindly thank all the authors who dedicated much of their time and efforts to contribute to the DBKDA 2011. We truly believe that, thanks to all these efforts, the final conference program consists of top quality contributions. This event could also not have been a reality without the support of many individuals, organizations, and sponsors. We are grateful to the members of the DBKDA 2011 organizing committee for their help in handling the logistics and for their work to make this professional meeting a success. We hope that DBKDA 2011 was a successful international forum for the exchange of ideas and results between academia and industry and for the promotion of progress in database research. We are convinced that the participants found the event useful and communications very open. The beautiful places of St. Maarten surely provided a pleasant environment during the conference and we hope you had a chance to visit the surroundings.
This work presents a disconnected transaction model able to cope with the increased complexity of longliving, hierarchically structured, and disconnected transactions. Wecombine an Open and Closed Nested Transaction Model with Optimistic Concurrency Control and interrelate flat transactions with the aforementioned complex nature. Despite temporary inconsistencies during a transaction’s execution our model ensures consistency.
Social Media
(2011)
In jüngerer Zeit gewinnt die Nutzung des Internet für das Inbound Marketing zunehmend an Bedeutung. Dabei liegt der Fokus auf den so genannten Social Media Plattformen wie Facebook, YouTube, MySpace, XING, LinkedIn, Twitter, SlideShare und Posterous. Die Entwicklung dieser Medien ist auf eine Veränderung bei der Nutzung des Internet zurückzuführen, die häufig unter dem Schlagwort Web 2.0 zusammengefasst wird. Das gewandelte Mediennutzungsverhalten der Kunden induziert Chancen und Risiken für das Marketing.
Das Internet gewinnt für das Marketing zunehmend an Bedeutung. Dabei liegt der Fokus auf sogenannten Social-Media-Anwendungen wie Facebook, Twitter oder XING. Für Unternehmen stellt sich die Frage, ob das veränderte Mediennutzungsverhalten der Kunden eine neue Marketinglogik induziert. Eine aktuelle Untersuchung gibt Einblicke in die Chancen und Risiken, Anwendungsbedingungen und Kontextfaktoren für die Nutzung von Social Media im Marketing.
The Fourth International Conference on Advances in Databases, Knowledge, and Data Applications [DBKDA 2012], held between February 29th and March 5th, 2012 in Saint Gilles, Reunion Island, continued a series of international events covering a large spectrum of topics related to advances in fundamentals on databases, evolution of relation between databases and other domains, data base technologies and content processing, as well as specifics in applications domains databases. Advances in different technologies and domains related to databases triggered substantial improvements for content processing, information indexing, and data, process and knowledge mining. The push came from Web services, artificial intelligence, and agent technologies, as well as from the generalization of the XML adoption. High-speed communications and computations, large storage capacities, and loadbalancing for distributed databases access allow new approaches for content processing with incomplete patterns, advanced ranking algorithms and advanced indexing methods. Evolution on e-business, e-health and telemedicine, bioinformatics, finance and marketing, geographical positioning systems put pressure on database communities to push the ‘de facto’ methods to support new requirements in terms of scalability, privacy, performance, indexing, and heterogeneity of both content and technology. We take here the opportunity to warmly thank all the members of the DBKDA 2012 Technical Program Committee, as well as the numerous reviewers. The creation of such a broad and high quality conference program would not have been possible without their involvement. We also kindly thank all the authors who dedicated much of their time and efforts to contribute to DBKDA 2012. We truly believe that, thanks to all these efforts, the final conference program consisted of top quality contributions. Also, this event could not have been a reality without the support of many individuals, organizations, and sponsors. We are grateful to the members of the DBKDA 2012 organizing committee for their help in handling the logistics and for their work to make this professional meeting a success. We hope that DBKDA 2012 was a successful international forum for the exchange of ideas and results between academia and industry and for the promotion of progress in the fields of databases, knowledge, and data applications. We are convinced that the participants found the event useful and communications very open. We also hope the attendees enjoyed the charm of Saint Gilles, Reunion Island.
Redirected walking techniques allow people to walk in a larger virtual space than the physical extents of the laboratory. We describe two experiments conducted to investigate human sensitivity to walking on a curved path and to validate a new redirected walking technique. In a psychophysical experiment, we found that sensitivity to walking on a curved path was significantly lower for slower walking speeds (radius of 10 meters versus 22 meters). In an applied study, we investigated the influence of a velocity-dependent dynamic gain controller and an avatar controller on the average distance that participants were able to freely walk before needing to be reoriented. The mean walked distance was significantly greater in the dynamic gain controller condition, as compared to the static controller (22 meters versus 15 meters). Our results demonstrate that perceptually motivated dynamic redirected walking techniques, in combination with reorientation techniques, allow for unaided exploration of a large virtual city model.
Das Motto der diesjährigen Konferenz lautet "Reality++: Tomorrow comes today!". Unter diesem fast schon visionären Thema werden die Ergebnisse der verschiedenen Vertiefungsarbeiten aus den vergangenen Monaten präsentiert. Das Programm wird vervollständigt durch Beiträge von Experten aus der Forschung und Industrie.