Berlin, Techn. University, Diss., 2007.

Berlin, Techn. Univ., Diss., 2005. / Computerdatei im Fernzugriff.

Many large business processes are inherently distributed, spanning multiple organizations, administrative domains, and geographic locations. To support such applications, this thesis develops a flexible and distributed platform to develop, execute, and monitor business processes. The solutions utilize a distributed content-based publish/subscribe overlay that is extended with support for mobile clients and client interest churn. Over this layer, a distributed execution engine uses events to coordinate the execution of the process, and dynamically redeploys activities in the process in order to minimize a user-specified cost function and preserve service level agreements (SLAs). Finally, a management layer allows users to find and automatically compose services available across a distributed set of service registries, and monitor processes for SLA violations. Evaluations show that the distributed execution engine can scale better than alternate architectures, exhibiting over 60% improvements in execution time in one experiment. As well the system can dynamically redeploy processes to reflect changing workload conditions and SLAs, saving up to 90% of the process messaging overhead of a static deployment.

Many large business processes are inherently distributed, spanning multiple organizations, administrative domains, and geographic locations. To support such applications, this thesis develops a flexible and distributed platform to develop, execute, and monitor business processes. The solutions utilize a distributed content-based publish/subscribe overlay that is extended with support for mobile clients and client interest churn. Over this layer, a distributed execution engine uses events to coordinate the execution of the process, and dynamically redeploys activities in the process in order to minimize a user-specified cost function and preserve service level agreements (SLAs). Finally, a management layer allows users to find and automatically compose services available across a distributed set of service registries, and monitor processes for SLA violations. Evaluations show that the distributed execution engine can scale better than alternate architectures, exhibiting over 60% improvements in execution time in one experiment. As well the system can dynamically redeploy processes to reflect changing workload conditions and SLAs, saving up to 90% of the process messaging overhead of a static deployment.

In the publish/subscribe paradigm, information providers disseminate publications to all consumers who have expressed interest by registering subscriptions. This paradigm has found wide-spread applications, ranging from selective information dissemination to network management. However, all existing publish/subscribe systems cannot capture uncertainty inherent to the information in either subscriptions or publications. In many situations the large number of data sources exhibit various kinds of uncertainties. Examples of imprecision include: exact knowledge to either specify subscriptions or publications is not available; the match between a subscription and a publication with uncertain data is approximate; the constraints used to define a match is not only content based, but also take the semantic information into consideration. All these kinds of uncertainties have not received much attention in the context of publish/subscribe systems. In this thesis, we propose new publish/subscribe models to express uncertainties and semantics in publications and subscriptions, along with the matching semantics for each model. We also develop efficient algorithms to perform filtering for our models so that it can be applied to process the rapidly increasing information on the Internet. A thorough experimental evaluation is presented to demonstrate that the proposed systems can offer scalability to large number of subscribers and high publishing rates.

The traditional book market matures, there are about 40,000 kinds of books published each year. But it is facing an oversupply situation. Return of a large number of books to make the traditional publishing business increasingly difficult. Online bookstores have established over ten years. Books are the most common products online shopping. The end of year 2010, a large number of sales for ebooks and e-reader. We can see that reading habits of human has begun to change. The reader can read thousands of books with an e-reader around everywhere. Publishers can sell books through the internet. How can the rise of e-reader? What will be affected for the traditional logistics providers and suppliers? Which new business models and benefits bring from e-reader and e-bookstore? This study used qualitative research to the literature review and case study, to observe and explain the e-reader how to affect the traditional suppliers and bring new benefits. Base on publishing ebooks through the internet, the digital platform service providers replace traditional logistics providers, suppliers, and publishers. Internet services provider replace the traditional logistics providers. Ebooks and e-reader use for reduce logistics costs and solve inventory problems. Consumer behavior changed to impact the traditional book industry, but also bring new economic benefits.

In the era of mobile cloud computing, the consumption of virtualized software and Web-based services from super-back-end infrastructure using smartphones and tablets is gaining much research attention from both the industry and academia. Nowadays, these mobile devices generate and access multimedia data hosted in social media and other sources in order to enhance the users’ multimedia experience. However, multimedia data is unstructured which can lead to challenges with data synchronization between these mobile devices and the cloud computing back-end. The issue with data synchronization is further fueled by the fact that mobile devices can experience intermittent connectivity losses due to unstable wireless bandwidths. While previous works proposed Simple Object Access Protocol (SOAP) -based middleware for the Web services’ synchronization, this approach is not efficient in a mobile environment because the SOAP protocol is verbose. Thus, the Representational State Transfer (REST) standard has been proposed recently to model the Web services since it is lightweight. This thesis proposes a novel approach for implementing a REST-based mobile Web Service for multimedia file sharing that utilizes a channel-based publish/subscribe communication scheme to synchronize smartphone or tablet-hosted NoSQL databases with a cloud-hosted NoSQL database. This thesis evaluates the synchronicity and the scalability of a prototype system that was implemented according to this approach. Also, this thesis assesses the overhead of the middleware component of the system.

In the publish/subscribe paradigm, information providers disseminate publications to all consumers who have expressed interest by registering subscriptions. This paradigm has found wide-spread applications, ranging from selective information dissemination to network management. However, all existing publish/subscribe systems cannot capture uncertainty inherent to the information in either subscriptions or publications. In many situations the large number of data sources exhibit various kinds of uncertainties. Examples of imprecision include: exact knowledge to either specify subscriptions or publications is not available; the match between a subscription and a publication with uncertain data is approximate; the constraints used to define a match is not only content based, but also take the semantic information into consideration. All these kinds of uncertainties have not received much attention in the context of publish/subscribe systems. In this thesis, we propose new publish/subscribe models to express uncertainties and semantics in publications and subscriptions, along with the matching semantics for each model. We also develop efficient algorithms to perform filtering for our models so that it can be applied to process the rapidly increasing information on the Internet. A thorough experimental evaluation is presented to demonstrate that the proposed systems can offer scalability to large number of subscribers and high publishing rates.

Techn. University, Diss., 2004--Darmstadt.

In this study a comparison of the publish-subscribe communication protocols OPS, MQTT and DDS were conducted. The implementation used for DDS was fastDDS and the client library Paho Eclipse MQTT C++ was used for MQTT with the broker implementation Eclipse Mosquitto. The goal was to see which out of these protocols performs best in a peer-to-peer communication scenario when it comes to latency and throughput with varying payload size. Two experiments were carried out. The first experiment measures the round-trip-time of a message and is realized by a ping-pong application. The latency was then calculated by taking half of the round-trip-time. The second experiment was publishing messages from one client and being retrieved by another and counting the amount of messages being retrieved in one second. To get bytes per second the payload size was multiplied by the amount of messages retrieved by the subscriber. The result of the first experiment showed that OPS with the underlying transport protocol TCP had the most favorable result. For the second experiment OPS with UDP as the transport protocol had the highest throughput in most cases however for the highest payload used in the experiment fastDDS with UDP had the highest throughput. However, the results gave substantial differences between the protocols in regards to throughput which indicate that the configuration might not be optimal for a fair comparison. Further research of this is recommended before making a final conclusion in regards to the overall results. / I denna studie genomfördes en jämförelse av kommunikationsprotokollen OPS, MQTT och DDS. Implementeringen som användes för DDS var fastDDS och klientbiblioteket Paho Eclipse MQTT C++ användes för MQTT med Eclipse Mosquitto som broker. Målet var att se vilket av dessa protokoll som fungerar bäst i ett peer-to-peer-kommunikationsscenario när det gäller fördröjningstid och throughput med varierande payloadstorlek. Två experiment utfördes. Det första experimentet mäter round-trip-time för ett meddelande och realiseras av en ping-pong-applikation. Fördröjningstiden beräknades sedan genom att ta hälften av round-trip-time. Det andra experimentet var att publicera meddelanden från en klient och mottas av en annan och räkna mängden meddelanden som mottas på en sekund. För att få byte per sekund multiplicerades payload storleken med mängden meddelanden som togs emot av prenumeranten. Resultatet av det första experimentet visade att OPS med det underliggande transportprotokollet TCP hade det mest gynnsamma resultatet. För det andra experimentet hade OPS med UDP som transportprotokoll den högsta throughput i de flesta fall, men för den största payloadstorleken som användes i experimentet hade fastDDS med UDP den högsta. Resultaten gav dock betydande skillnader mellan protokollen när det gäller throughput som indikerar att konfigurationen kanske inte är optimal för en rättvis jämförelse. Ytterligare forskning om detta rekommenderas för att utreda orsaken till dessa skillnader och därefter kunna skapa konfigurationer som ger rättvisa förutsättningar för en optimal jämförelse.