Concealing Presence Information in Instant Messaging Systems
- Information about online presence allows participants of instant messaging (IM) systems to determine whether their prospective communication partners will be able to answer their requests in a timely manner, or not. That is why presence information, combined with the ability to send instant messages, makes IM more personal and closer than other forms of communication such as e-mail. On the other hand, revelation of presence constitutes a potential of misuse by untrustworthy entities. A possible risk is the generation of online logs disclosing user habits. This makes presence information a resource worth protecting. We argue, however, that current IM systems do not take reasonable precautions to protect presence information. We implemented an IM system designed to be robust against attacks to disclose a user’s presence. In contrast to existing systems, it stores presence information in a registry in a way that is only detectable and applicable for intended users and not comprehensible even for the registry itself. We use a distributed hash table (DHT) as registry and apply an anonymous communication network to protect the physical addresses of both senders and receivers of messages.
Modelling and Validating Business Collaborations: A Case Study on RosettaNet
- The way business processes are organised heavily influences the flexibility and the expenses of enterprises. The capability to address changing market needs in a timely manner and to provide appropriate pricing is indispensable in a world of internationalisation and growing competition. Optimising processes that cross enterprise boundaries potentially is a key success factor in achieving this goal but it requires the information systems of the participating enterprises to be consistently integrated. This gives rise to some challenging tasks. The personnel involved in building up business collaborations comes from different enterprises with different business vocabulary and background which requires extensive communication support. The lack of central technical infrastructure, typically prohibited by business politics, often calls for a distributed and computer-aided collaboration structure, so that the resulting complexity must be handled somehow. Nevertheless robustness is an important factor in building business collaborations as these may exchange goods of considerable value. This technical report proposes the use of a two step modelling approach that separates business logic, modelled in the so-called centralised perspective (CP), from its distributed implementation, modelled in the so-called distributed perspective (DP). The separation of these perspectives enables business people to concentrate on business issues and to solve communication problems in the CP whereas technical staff can concentrate on distribution issues. The use of stringent modelling rules is advised in order to provide the basis for formal analysis techniques as one means to achieve robustness. Considering the choreography of RosettaNet Partner Interface Processes (PIPs) as the subject of my analysis, UML activity diagrams for modelling the CP and WSBPEL for modelling the DP are described as enabling techniques for implementing the proposed two step modelling approach. Further, model checking is applied to validate the CP and DP models in order to detect errors in early design phases. As the adequacy of model checking tools highly depends on the detailed modelling techniques as well as the properties to be checked, a major part of our discussion covers relevant properties and requirements for a model checker.
Terrorismus und Terrorismusbekämpfung, Seminarband
- Im ersten Teil werden die Organisation von Al Qaida analysiert und die Vorgehensweise beim Anschlag am 11. September rekonstruiert sowie Lücken bei der Terrorismusbekämpfung aufgezeigt. Im zweiten Teil werden die programmatischen und institutionellen Änderungen seit 9/11 insbesondere in den USA vorgestellt und kritisch beleuchtet.
Adult education in Germany : roots, status, mainstreams, changes
- With its many traditions, roots, and facets, adult education in Germany is in a developmental stage marked by variety - various institutions, programs, aims and ideas, parallel developments and competition. Adult education providers show little cooperation and coordination among themselves. They are often unaware of other providers that comprise the full scope of the field. Some of the developments can only be understood in the context of German culture, history, and economy. Two central arguments are given in comparative adult education to explain the value of trying to understand adult education practices in other countries (Reischmann, Bron, Jelenc, 1999). On a practical level, “borrowing” is expected to help us adapt successful foreign practices and integrate them into our own practical work - and avoid mistakes and “reinventing the wheel”. On a theoretical level, the international-comparative perspective can help us to overcome ethnocentric blindness, helping us, irritated by observations in a foreign context, to better perceive and understand our own field and system. Certainly cultural differences limit the transfer from one country to another. Comparative research, by helping to understand the differences and similarities as well as their significance for adult education, can clarify the possibilities and limits of understanding and borrowing. Both are indispensable in a world where in many countries experiences in the various fields of adult education are gained and needed.