Suggested Approach
To overcome the previously identified problem, XML
[3] should be used as a standard data interchange format.
XML documents can contain all required information from simple messages to complex maps. Furthermore it is flexible in the handling of evolving data structures. A disadvantage of XML might be long tag names and white space, increasing the document size. But the intel-
ligent selection of tag names in the design phase and compression will reduce the document size significantly. The efficient usage of communication channels is based on a continuous and balanced transmission of data to avoid communication peaks. Hence intelligent caching, pre-fetching and selection of XML documents are the core technology for the implementation of mobile data management. Caching allows for effective usage of communication bandwidth by avoiding retransmission of mostly static information. Intelligent prefetching and selection strategies are used for timely delivery of complex location related information, e.g. maps of buildings.
The reliability of the system is increased by redundant storage of XML documents on different devices (peers). Hence information has to be replicated in a peer to peer manner among nearby devices. This decreases the probability of information loss in the case of a communication failure because other devices can be used as an
"information router". Vice versa, in this way it is possible to avoid the loss of important sensor information. For the proposed technologies data integrity and timeliness of information are important. A distributed transaction management, which is adapted to the special needs in disaster management, ensures that instructions or technical descriptions are completely transmitted to the receiver. Notifications of incomplete transmissions are necessary. The caching strategy has to take the timeliness level of information into account, e.g. static maps have to be updated less frequently than instructions.