SFB 627: Nexus
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SFB 627: Nexus
Project A2:

Model-Based Communication

Deutsche Version
Prof. Dr. rer. nat. Dr. h. c. Kurt Rothermel

University of Stuttgart
Institute of Parallel and Distributed Systems
Universitätsstraße 38
70569 Stuttgart

Tel. +49 (0)711 7816 434
Fax +49 (0)711 7816 424


In the project A2 "Model-Based Communication", we develop communication mechanisms that utilize the world model in order to make communication more efficient or even make new forms of communication possible. Research areas are the support of disconnected operation and geographic communication (geocast). Another issue, which is closely related, is event-based communication that deals with the observation and propagation of events defined on the basis of the world model. This research is funded by an external cooperation with Microsoft Research.

Based upon the results of the Nexus Research Group, mechanisms are developed to facilitate the access to information objects of the world model in disconnected operation. We will use an approach called hoarding, i.e. the prefetching of information objects a user will need in the future in areas with good access to communication networks. The hoarding mechanism is based on the use of so-called infostations that provide cheap and fast access to the world model and other sources of information through wireless LANs (WLANs). They are embedded in an area, where wireless communication is either not possible or only at the speed of GPRS or -- in the future -- UMTS. Thus, the research objective is to develop hoarding mechanisms that select the information objects relevant to a user and pre-load them onto the mobile device. By considering the location dependency and semantic distance of information objects as well as the characteristics and current situation of a user, a high relevance of pre-loaded data and a low number of "hoard misses" (i.e. when an information object is requested that had not been hoarded before) shall be achieved. The semantic distance of spatial objects is determined by analyzing the structural information and existing relations of the world model. This results in totally new questions of how to hold parts of the world model ready on mobile devices. Additionally, suitable broadcast mechanisms ("broadcast discs", "indexing on air") optimize the transfer of selected information objects from the infostation to the mobile device.

The second research area of this project deals with concepts and implementations of protocols for geographic communication. These protocols give the user the possibility to send messages to receivers in a certain geographic area, i.e. the group of receivers is determined by the target area of the message and the current geographic position of the receiver. Geocast is supported by a detailed world model that allows fine-grained (geographic) addressing and therefore the usage of geocast in urban areas. Broadcast protocols, i.e. protocols for sending messages to all receivers in a certain area, are studied as well as geographic multicast protocols that deliver messages only to a certain group of receivers defined by additional attributes. Especially the latter benefits considerably from the detailed information of the world model. Beside best effort protocols, protocols for reliable geocast will be developed.


- Institute of Parallel and Distributed Systems    
  Distributed Systems Research Group    


- Project Head    
 - Prof. Dr. rer. nat. Dr. h. c. Kurt Rothermel   
- Research Assistants    
 - Dipl.-Inf. Martin Bauer   
 - Dipl.-Inf. Susanne Bürklen   
 - Dipl.-Inf. Frank Dürr