Alexander Leonhardi

Next century challenges: Nexus—an open global infrastructure for spatial-aware applications

Due to the lack of a generic platform for locationand spatial-aware systems, many basic services have to be reimplemented in each application that uses spatial-awareness. A cooperation among different applications is also difficult to achieve without a common platform. In this paper we present a platform that solves these problems. It provides an infrastructure that is based on digital models of regions of the physical world, which are augmented by virtual objects. We show how virtual objects make the integration of existing information systems and services in spatial-aware systems easier. Furthermore, our platform supports interactions between the computer models and the real world and integrates single models in a global “Augmented World”.

A Comparison of Protocols for Updating Location Information

Detailed location information of mobile objects, for example that of a user with a mobile computer or phone, is an important input for many location-aware applications. However, constantly updating the location information for thousands of mobile objects is not feasible. Therefore, special update protocols for location information are required that transmit the information as efficiently as possible, that is requiring only few update messages, while still being effective in returning the location information with the desired accuracy. Different classes of such update protocols are described in this paper and a new combined protocol is proposed. To be able to compare their effectiveness and efficiency, we present an analysis for the minimum and average resulting accuracy of the location information in comparison with the number of messages transmitted. We also present the results of simulations that we have performed to back up our analysis.

Architecture of a large-scale location service

Location-aware services are a promising way of exploiting the special possibilities created by ubiquitous mobile devices and wireless communication. Advanced location-aware applications will require highly accurate information about the geographic location of mobile objects and functionality that goes beyond simply querying the users position, for example determining all mobile objects inside a certain geographic area. In this paper, we propose a generic large-scale location service, which has been designed with the goal of managing the highly dynamic location information for a large number of mobile objects, thus providing a common infrastructure that can be employed by location-aware applications. We propose a hierarchical distributed architecture, which can efficiently process these queries in a scalable way. To be able to deal with the frequent updates and queries resulting from highly dynamic location information, we propose a data storage component, which makes use of a main memory database.

A map-based dead-reckoning protocol for updating location information

An important aspect of location-aware services is the management of location information. To this end, location information needs to be transferred from a mobile device, which determines this information by means of a local positioning sensor (such as GPS), to a location service, where the location information can be queried by applications. Because bandwidth in wide area mobile communications is still scarce and expensive, it is important to use an update protocol that requires as few messages as possible while still guaranteeing a desired accuracy of the location information. To decrease the number of necessary update messages, so-called dead-reckoning strategies have been proposed. In this paper we give an overview of different variants of dead-reckoning protocols for updating location information and propose a new map-based protocol. While a simple dead-reckoning protocol already reduces the number of update messages in some cases by up to 83%, the map-based protocol further reduces their number by again up to 60% and is able to sustain these improvements for non-uniform movement.

Protocols for Updating Highly Accurate Location Information

In this chapter, we have provided a classification of protocols that are suitable for continuously transmitting highly accurate location information. We have discussed different protocol variants and compared them according to their effectiveness and efficiency for characteristic types of mobile objects. Especially the class of dead-reckoning protocols has the potential to reduce the number of required update messages, while still being able to guarantee a certain requested accuracy. More advanced dead-reckoning protocols (such as a map-based protocol) promise to reduce the number of required messages still further.

Development of Problem-Specific Evolutionary Algorithms

It is a broadly accepted fact that evolutionary algorithms (EA) have to be developed problem-specifically. Usually this is based on experience and experiments. Though, most EA environments are not suited for such an approach. Therefore, this paper proposes a few basic concepts which should be supplied by modern EA simulators in order to serve as a toolkit for the development of such algorithms.

Metaphors and Context-Aware Information Access

Abstract: Metaphors are often used to provide the user with a mental model to ease the use of computers. An example of such a metaphor is the commonly used “Desktop Metaphor”. Metaphors also can be used to ease context-aware information access for the users of mobile information systems. In this paper we present a taxonomy that allows the categorisation of such metaphors. Furthermore, we give an overview of existing metaphors and their implementations. After introducing some new metaphors we conclude our considerations with a classification of new and existing metaphors using our taxonomy.