[Show abstract][Hide abstract] ABSTRACT: Context management systems are expected to administrate large volumes of spatial and non-spatial information in geographical disperse domains. In particular, when these systems cover wide areas such as cities, countries or even the entire planet, the design of scalable storage, retrieval and propagation mechanisms is paramount. This paper elaborates on mechanisms that address advanced requirements, including support for distributed context databases management; efficient query handling; innovative management of mobile physical objects and optimization strategies for distributed context data dissemination. These mechanisms establish a robust spatially-enhanced distributed context management framework that has already been designed and carefully implemented and thoroughly evaluated.
Pervasive and Mobile Computing. 01/2010; 6:218-238.
[Show abstract][Hide abstract] ABSTRACT: In ubiquitous computing environments, context management systems are expected to administrate large
volumes of spatial and non-spatial information in geographical disperse domains. In particular, when
these systems cover wide areas such as cities, countries or even the entire planet, the design of scalable
storage, retrieval and propagation mechanisms is paramount. This chapter elaborates on mechanisms
that address advanced requirements including support for distributed context databases management;
efficient query handling; innovative management of mobile physical objects and optimization strategies
for distributed context data dissemination. These mechanisms establish a robust spatially-enhanced
distributed context management framework that has thoroughly been designed, carefully implemented
and extensively evaluated via numerous experiments.
[Show abstract][Hide abstract] ABSTRACT: Pervasive computing systems need to be strongly proactive. Context-awareness contributes to this, thus minimizing human-machine interaction. Context-aware systems are greatly enhanced by the utilization of recorded history of the users' situations and interactions. In this paper, an approach is proposed for modelling, storing and exploiting history-of-context, in order to predict or estimate context information. The proposed framework is context-type-independent, requires minimal processing and storage resources, and can be used for data compression. It is based on multiple context prediction rule generation models, demonstrates high prediction success ratio, and has been empirically evaluated via extensive experiments.
Proceedings of the 3rd international workshop on Services integration in pervasive environments; 07/2008
[Show abstract][Hide abstract] ABSTRACT: Context management systems collect large volumes of spatial and non-spatial information. In particular, when these systems cover large areas like cities, countries or even the entire planet, the design of scalable storage, retrieval and delivery mechanisms is paramount. The Daidalos context management system has been design to meet the requirements of large scale systems. This paper presents the Daidalos approach for a scalable distributed data management approach. The system architecture, the management of mobile database nodes and federation issues are described.
Mobile and Wireless Communications Summit, 2007. 16th IST; 08/2007
[Show abstract][Hide abstract] ABSTRACT: The emerging pervasive computing services will eventually lead to the establishment of a context marketplace, where context consumers will be able to obtain the information they require by a plethora of context providers. In this marketplace, several aspects need to be addressed, such as: support for flexible federation among context stakeholders enabling them to share data when required; efficient query handling based on navigational, spatial or semantic criteria; performance optimization, especially when management of mobile physical objects is required; and enforcement of privacy and security protection techniques concerning the sensitive context information maintained or traded. This paper presents mechanisms that address the aforementioned requirements. These mechanisms establish a robust spatially-enhanced distributed context management framework and have already been designed and carefully implemented.
[Show abstract][Hide abstract] ABSTRACT: The challenge of saturating all phases of pervasive service provision with context-aware functionality lies in coping with
the complexity of maintaining, retrieving and distributing context information. To efficiently represent and query context
information a sophisticated modelling scheme should exist. To distribute and synchronise context knowledge in various context
repositories across a multitude of administrative domains, streamlined mechanisms are needed. This paper elaborates on an
innovative context management framework that has been designed to cope with free-text and location based context retrieval
and efficient context consistency control. The proposed framework has been incorporated in a multi-functional pervasive services
platform, while most of the mechanisms it employs have been empirically evaluated.
Journal of Network and Systems Management 01/2007; 15:57-74. · 0.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Context awareness is an essential cornerstone in future pervasive computing systems. It has the potential to greatly reduce the user attention and interaction bottlenecks, to give humans the impression that services fade into the background, and to support intelligent personalization features. Nevertheless, in order to create such an environment, a growing amount of personal information has to be provided to the system, either manually or automatically. Hence the digital trace and representation users have in the system is getting dangerously detailed, thus stressing the need for privacy protection. DAIDALOS (Satyanarayanan, 2001) is a European research project in the area of 3G and beyond, which aims to combine heterogeneous networks in a transparent and seamless way, and develop on top of this a pervasive environment for applications and end-users. This paper describes the main models and mechanisms that have been established to provide federated context-aware services and protect the privacy of their users
Pervasive Services, 2006 ACS/IEEE International Conference on; 07/2006
[Show abstract][Hide abstract] ABSTRACT: Context awareness is an inherent feature of pervasive computing. It enhances the proactiveness of the system thus requiring less user attention and fewer human-machine interactions, it supports intelligent personalization features, and it can assist the system to address the user requirements considering the current conditions. Nevertheless, in such environments, various types of context information are involved and need to be efficiently managed and maintained, soundly interpreted, rapidly processed, and securely disseminated by the system. Thus, an interoperable and flexible context representation scheme is necessary that will support efficient context interpretation and reasoning and will perform well in distributed large-scale context-aware systems. This paper is concerned with the development of a hybrid context representation scheme that aims to combine the maintenance, distribution and administrative facilities of a location-based context model and the semantic advantages of context ontologies.
Pervasive Computing and Communications Workshops, 2006. PerCom Workshops 2006. Fourth Annual IEEE International Conference on; 04/2006
[Show abstract][Hide abstract] ABSTRACT: Context awareness is one of the key aspects of pervasive computing systems. In such systems, a plethora of dynamic context information needs to be constantly retrieved, soundly interpreted, rapidly processed, maintained in various repositories, and securely disseminated. Thus, a flexible, scalable and interoperable context representation scheme needs to be established and solid context management mechanisms need to be adopted, which will perform well in large-scale distributed pervasive systems. This paper elaborates on the COMPACT context middleware that has been designed to cope with the issues above and saturate pervasive computing environments with context awareness functionality.
International Journal of Pervasive Computing and Communications 01/2006; 2:229-246.
[Show abstract][Hide abstract] ABSTRACT: Context-based applications are supposed to decrease human- machine interactions. To this end, they must interpret the meaning of context data. Ontologies are a commonly accepted approach of spec- ifying data semantics and are thus considered a precondition for the implementation of context-based systems. Yet, experiences gained from the European project Daidalos evoke concerns that this approach has its flaws when the application domain can hardly be delimited. These concerns are raised by the human limitation in dealing with complex specifications. This paper proposes a relaxation of the situation: Humans strength is the understating of natural languages, computers, however, possess su- perior pattern matching power. Therefore, it is suggested to enrich or even replace semantic specifications of context data items by free-text descriptions. For instance, rather than using an Ontology specification to describe an Italian restaurant the restaurant can simply be described by its menu card. To facilitate this methodology, context documents are introduced and a novel information retrieval approach is elucidated, evaluated, and anal- ysed with the help of Bose-Einstein statistics. It is demonstrated that the new approach clearly outperforms conventional information retrieval engines and is an excellent addition to context Ontologies.
Location- and Context-Awareness, Second International Workshop, LoCA 2006, Dublin, Ireland, May 10-11, 2006, Proceedings; 01/2006
[Show abstract][Hide abstract] ABSTRACT: Context-awareness and personalisation are important concepts that are essential cornerstones in future systems providing pervasive services. These two concepts are closely interrelated and dependent on each other for fully functional context-aware personalised services. Daidalos is a European research project in the area of 3G and beyond, which aims to combine heterogeneous networks in a transparent and seamless way, and develop a pervasive environment for applications and end-users on top of this. The first phase of implementation has produced a basic system that is currently being developed further. This paper outlines the basic pervasive service platform architecture and describes the context-awareness and personalisation features that are being implemented in Daidalos.
Pervasive Services, 2005. ICPS '05. Proceedings. International Conference on; 08/2005
[Show abstract][Hide abstract] ABSTRACT: Services in pervasive computing systems must evolve so that they become minimally intrusive and exhibit inherent proactiveness
and dynamic adaptability to the current conditions, user preferences and environment. Con-text awareness has the potential
to greatly reduce the human attention and interaction bottlenecks, to give the user the impression that services fade into
the background, and to support intelligent personalization and adaptability features. To establish this functionality, an
infrastructure is required to collect, manage, maintain, synchronize, infer and disseminate context information towards applications
and users. This paper presents a context model and ambient context management system that have been integrated into a pervasive
service platform. This research is being carried out in the DAIDALOS IST Integrated Project for pervasive environments. The
final goal is to integrate the platform developed with a heterogeneous all-IP network, in order to provide intelligent pervasive
services to mobile and non-mobile users based on a robust context-aware environment.
Location- and Context-Awareness, First International Workshop, LoCA 2005, Oberpfaffenhofen, Germany, May 12-13, 2005, Proceedings; 01/2005
[Show abstract][Hide abstract] ABSTRACT: Since agents have the ability to migrate to outperforming resources they can potentially balance the load of heterogeneous
systems. However, to balance resources efficiently agents must take the load into account. Thus, to support the agent migration
strategy the application of server selection systems has been proposed recently. Server selection systems keep track of the
load of network and host resources and hence predict the performance of different migration strategies. Yet, server selection
comes at a cost and therefore agents must take care when applying it. This paper presents a decision strategy for the agent’s
decision problem. The performance of the approach is analysed with the help of a simple queuing model.
NETWORKING 2004, Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communication, Third International IFIP-TC6 Networking Conference, Athens, Greece, May 9-14, 2004, Proceedings; 01/2004
[Show abstract][Hide abstract] ABSTRACT: As mobile agents can dynamically adapt to resource capacities they suit heterogeneous environments. That is, agents are not bound to a single host and can migrate to an outperforming one. Consequently, agent technology can balance the resources of a heterogeneous system. However, to balance resources efficiently agents must take resource load into account. Thus, to support the agent migration strategy the application of server selection systems has been proposed recently. Server selection systems keep track of the load of network and host resources and hence predict the performance of different migration strategies. Yet, server selection comes at a cost and therefore agents must take care when applying it. This paper presents a server selection system which meets the requirements of mobile agents. Moreover, in contrast to any other server selection system known from literature the new one addresses the problem of rational server selection.
Computers and Communications, 2004. Proceedings. ISCC 2004. Ninth International Symposium on; 01/2004
[Show abstract][Hide abstract] ABSTRACT: As mobile agents have the ability to operate autonomously and in a disconnected way they are considered to suit mobile computing
environments. Mobile users can dispatch agents into the fixed network where the agents operate in the users behalf. Thus,
in contrast to client/server interactions agents do not suffer from poor performing wireless access networks. In this paper
the performance of mobile agents and client/server interactions are analysed with respect to heterogeneous networks and server
resources. It is argued that without a certain knowledge of the available resources agents can hardly decide whether they
should migrate or just apply client/server calls to access a remote service. To this end, it is proposed that agents should
access server selection systems in order to plan their migration strategy. However, while server selection systems process
agent requests the agents are waiting idle. Thus, access to server selection systems comes at a cost and therefore agents
must be careful about it. To solve this decision problem an algorithm is proposed which estimates the benefits of accessing
server selection systems. Finally, the decision algorithm is evaluated with the help of a simulation model.
Distributed Applications and Interoperable Systems, 4th IFIP WG6.1 International Conference, DAIS 2003, Paris, France, November 17-21, 2003, Proceedings; 01/2003
[Show abstract][Hide abstract] ABSTRACT: With their special ability to operate disconnected and autonomously mobile agents are well suited for wireless access networks:
Mobile user can dispatch mobile agents to the fixed network where they operate autonomously in the user’s behalf. While the
agent operates in the fixed network the user’s mobile device disconnects. Reconnection is only required when the agent needs
user feedback or returns results. Thus, mobile agents have the ability to save wireless network resources. While agents operate
disconnected they require a certain knowledge of the user’s preferences for service trading. But user preferences might change
frequently and thus agents require a central information storage which provides up to date user preference descriptions. In
this paper we propose the User Agent which manages user profile entries and acts as the user’s central service trader. Agents
can request services at the User Agent which correspond to the user’s preferences.
Advances in Artificial Intelligence. PRICAI 2000 Workshop Reader, Four Workshops held at PRICAI 2000, Melbourne, Australia, August 28 - September 1, 2000, Revised Papers; 01/2000