Stefan Böttcher

Learn More
While traditional fixed-wired network protocols like 2Phase-Commit guarantee atomicity, we cannot use them in mobile low bandwidth networks where network partitioning, node failure, and message loss may result in blocking. To deploy traditional database applications easily into a mobile environment, there is a demand for a protocol which guarantees an(More)
E-government webs are among the largest webs in existence, based on the size, number of users and number of information providers. Thus, creating a Semantic Web infrastructure to meaningfully organise e-government webs is highly desirable. At the same time, the complexity of the existing e-government implementations also challenges the feasibility of(More)
Applications using XML for data representation very often use different XML formats and thus require the transformation of XML data. The common approach transforms entire XML documents from one format into another, e.g. by using an XSLT stylesheet. Different from this approach, we use an XSLT stylesheet in order to transform a given XPath query or a given(More)
In traditional fixed-wired networks, standard protocols like 2-Phase-Commit are used to guarantee atomicity for distributed transactions. However, within mobile networks, a higher probability of failures including node failures, message loss, and even network partitioning makes the use of these standard protocols difficult or even impossible. To use(More)
Atomic commit protocols for distributed transactions in mobile ad-hoc networks have to consider message delays and network failures. We consider ad-hoc network scenarios, in which participants hold embedded databases and offer services to other participants. Services that are composed of several other services can access and manipulate data of physically(More)
Relational databases use predicates for a large variety of different functions. some leading to database search, others being handled by theorem proving. First we demonstrate that the theorem provinr! applications have very similar basic requirements for predicate manaeement but differ in their need foti efficiency. Second we Gresent dedicated deduction(More)
The computation of the union operator for different distributed datasets involves two challenges when participants are curious and can even act malicious: guaranteeing anonymity and guaranteeing security. Anonymity means that the owner of a certain data item cannot be identified provided that more than two participants act. Security means that no(More)
Whenever queries have to be evaluated on XML data streams or when the memory that is available to evaluate the XML data is relatively small compared to the document DOM based approaches that have to load and store large parts of the document in main memory will fail. In comparison, we present an approach to evaluate XPath queries on SAX streams that(More)