Matt Duckham

A formal model of obfuscation and negotiation for location privacy

Obfuscation concerns the practice of deliberately degrading the quality of information in some way, so as to protect the privacy of the individual to whom that information refers. In this paper, we argue that obfuscation is an important technique for protecting an individuals location privacy within a pervasive computing environment. The paper sets out a formal framework within which obfuscated location-based services are defined. This framework provides a computationally efficient mechanism for balancing an individuals need for high-quality information services against that individuals need for location privacy. Negotiation is used to ensure that a location-based service provider receives only the information it needs to know in order to provide a service of satisfactory quality. The results of this work have implications for numerous applications of mobile and location-aware systems, as they provide a new theoretical foundation for addressing the privacy concerns that are acknowledged to be retarding the widespread acceptance and use of location-based services.

Foundations of Geographic Information Science

Geographic Information Science. The Nature and Value of Geographic Information. Communicating Geographic Information in Context. Pragmatic Information Content. Representational Commitment in Maps. Granularity in Change over Time. A Theory of Granular Partitions. On the Ontological Status of Geographical Boundaries. Regions in Geography. Neighborhoods and Landmarks. Geographical Terminology Servers. Placing Cultural Events and Documents. Geographic Activity Models.

Including landmarks in routing instructions

This article addresses the problem of incorporating cognitively salient landmarks in computer-generated navigation instructions. On the basis of a review of the existing literature in the domain of navigation with landmarks, the article develops algorithms for generating routing instructions that include references to landmarks. The most basic algorithm uses a new weighting model to annotate simple routes with references to landmarks. A key novel feature of this algorithm is that it depends only on commonly available data and generic capabilities of existing web mapping environments. A suite of extensions are also proposed for improving the cognitive ergonomics of the basic landmark instructions. A case study, implemented within a national online routing system, demonstrates practicality of the approach. The article then concludes by reviewing a range of further issues for future work.

Monitoring qualitative spatiotemporal change for geosensor networks

Recent technological advances in geosensor networks demand new models of distributed computation with dynamic spatial information. This paper presents a computational model of spatial change in dynamic regions (such as may be derived from discretizations of continuous fields) founded on embeddings of graphs in orientable surfaces. Continuous change, connectedness and regularity of dynamic regions are defined and local transition rules are used to constrain region evolution and enable more efficient inference of a regions state. The model provides a framework for the detection of global high‐level events based on local low‐level ‘snapshot’ spatiotemporal data. The approach has particular relevance to environmental monitoring with geosensor networks, where technological constraints make the detection of global behaviour from local conditions highly advantageous.

Monitoring dynamic spatial fields using responsive geosensor networks

Information about dynamic spatial fields, such as temperature, windspeed, or the concentration of gas pollutant in the air, is important for many environmental applications. At the same time, the development of geosensor networks (wirelessly communicating, sensor-enabled, small computing devices distributed throughout a geographic environment) present new opportunities for monitoring dynamic spatial fields in much greater detail than ever before. This paper develops a new model for querying information about dynamic spatial fields using geosensor networks. In order to manage the inherent complexity of dynamic geographic phenomena, our approach is to focus on the qualitative representation of spatial entities, like regions, boundaries, and holes, and of events, like splitting, merging, appearance, and disappearance. Based on combinatorial maps, we present a qualitative model as the underlying data management paradigm for geosensor networks. This model is capable of tracking salient changes in the network in an energy-efficient way. Further, our model enables reconfiguration of the geosensor network in response to changes in the environment. We present an algorithm capable of adapting sensor network granularity according to dynamic monitoring requirements. Regions of high variability can trigger increases in the geosensor network granularity, leading to more detailed information about the dynamic field. Conversely, regions of stability can trigger a coarsening of the sensor network, leading to efficiency increases in particular with respect to power consumption and longevity of the sensor nodes. Querying of this responsive geosensor network is also considered, and the paper concludes with a review of future research directions.

Simulation of obfuscation and negotiation for location privacy

Current mobile computing systems can automatically sense and communicate detailed data about a persons location. Location privacy is an urgent research issue because concerns about privacy are seen to be inhibiting the growth of mobile computing. This paper investigates a new technique for safeguarding location privacy, called obfuscation, which protects a persons location privacy by degrading the quality of information about that persons location. Obfuscation is based on spatial imperfection and offers an orthogonal approach to conventional techniques for safeguarding information about a persons location. Imprecision and inaccuracy are two types of imperfection that may be used to achieve obfuscation. A set of simulations are used to empirically evaluate different obfuscation strategies based on imprecision and inaccuracy. The results show that obfuscation can enable high quality of service in concert with high levels of privacy.

An algebraic approach to automated geospatial information fusion

This paper presents a new technique for information fusion. Unlike most previous work on information fusion, this paper explores the use of instance‐level (extensional) information within the fusion process. This paper proposes an algorithm that can be used automatically to infer the schema‐level structure necessary for information fusion from instance‐level information. The approach is illustrated using the example of geospatial land‐cover data. The method is then extended to operate under uncertainty, such as in cases where the data are inaccurate or imprecise. The paper describes the implementation of the fusion method within a software prototype. Finally, the paper discusses several key topics for future research, including applications of this work to spatial‐data mining and the semantic web.

Information Dissemination in Mobile Ad-Hoc Geosensor Networks

This paper addresses the issue of how to disseminate relevant information to mobile agents within a geosensor network. Conventional mobile and location-aware systems are founded on a centralized model of information systems, typified by the client-server model used for most location-based services. However, in this paper we argue that a decentralized approach offers several key advantages over a centralized model, including robustness and scalability. We present an environment for simulating information dissemination strategies in mobile ad-hoc geosensor networks. We propose several strategies for scalable, peer-to-peer information exchange, and evaluate their performance with regard to their ability to distribute relevant information to agents and minimize redundancy.

Identifying factors of geographic event conceptualisation

The present paper examines whether the formal topological characterisation of spatial relations between moving geographic regions provides an adequate basis for the human conceptualisation of motion events for those regions. The paper focuses on gradual changes in topological relationships caused by continuous transformations of the regions (specifically, translations). Using a series of experiments, the conceptualisation and perception of conceptual neighborhoods is investigated. In particular, the role of conceptual neighborhoods in characterising motion events is scrutinised. The experiments employ a grouping paradigm and a custom‐made tool for presenting animated icons. The analysis examines whether paths through a conceptual neighborhood graph sufficiently characterise the conceptualisation of the movement of two regions. The results of the experiments show that changes in topological relations—as detailed by paths through a conceptual neighborhood graph—are not sufficient to characterise the cognitive conceptualisation of moving regions. The similarity ratings show clear effects of perceptually and conceptually induced groupings such as identity (which region is moving), reference (whether a larger or a smaller region is moving), and dynamics (whether both regions are moving at the same time).

Qualitative reasoning about consistency in geographic information

This paper explores the development and use of a qualitative reasoning system for describing consistency between different geographic data sets. Consistency is closely related to issues of uncertainty and interoperability in geographic information, and the paper assesses how automated reasoning about consistency can be used to support the integration of heterogeneous geographic data sets. The system developed is based on description logic. The decidability and tractability characteristics of description logic allow consistency checking to be deferred during data integration, so minimizing the information loss that usually accompanies any data integration task. Further, the user interface allows users to negotiate with the system in defining consistency. The results of the research suggest that further work could significantly increase the level of automation for many geographic data integration tasks.