"Grid" computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high-performance orientation. In this article, we define this new field. First, we review the "Grid problem," which we define as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources---what we refer to as virtual organizations. In such settings, we encounter unique authentication, authorization, resource access, resource discovery, and other challenges. It is this class of problem that is addressed by Grid technologies. Next, we present an extensible and open Grid architecture,inwhich protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing. We describe requirements that we believe any such mechanisms must satisfy and we discuss the importance of defining a compact set of intergrid protocols to enable interoperability among different Grid systems. Finally, we discuss how Grid technologies relate to other contemporary technologies, including enterprise integration, application service provider, storage service provider, and peer-to-peer computing. We maintain that Grid concepts and technologies complement and have much to contribute to these other approaches.

Ubiquitous computing poses a number of challenges for software architecture.

Hive is a distributed agents platform, a decentralized system for building applications by networking local system resources. This paper presents the architecture of Hive, concentrating on the idea of an "ecology of distributed agents" and its implementation in a practical Java based system. Hive provides ad-hoc agent interaction, ontologies of agent capabilities, mobile agents, and a graphical interface to the distributed system. We are applying Hive to the problems of networking "Things That Think," putting computation and communication in everyday places such as your shoes, your kitchen, or your own body. TTT shares the challenges and potentials of ubiquitous computing and embedded network applications. We have found that the flexibility of a distributed agents architecture is well suited for this application domain, enabling us to easily build applications and to reconfigure our systems on the fly. Hive enables us to make our environment and network more alive.

CoolTown offers a web model for supporting nomadic users, based on the convergence of web technology, wireless networks and portable devices. This paper describes how CoolTown ties web resources to physical objects and places, and how users interact with resources using the information appliances they carry, from laptops to smart watches. Enabling the automatic discovery of URLs from our physical surroundings, and using localized web servers for directories, we create location-aware but ubiquitous systems. On top of this infrastructure we leverage device connectivity to support communication services. Keywords Web presence; nomadic computing; location-aware computing; ubiquitous computing; resource discovery. 1.

Abstract. An increasing number of distributed applications will be written for mobile hosts, such as laptop computers, third generation mobile phones, personal digital assistants, watches and the like. Application engineers have to deal with a new set of problems caused by mobility, such as low bandwidth, context changes or loss of connectivity. During disconnection, users will typically update local replicas of shared data independently from each other. The resulting inconsistent replicas need to be reconciled upon re-connection. To support building mobile applications that use both replication and reconciliation over ad-hoc networks, we have designed xmiddle, a mobile computing middleware. In this paper we describe xmiddle and show how it uses reflection capabilities to allow application engineers to influence replication and reconciliation techniques. xmiddle enables the transparent sharing of XML documents across heterogeneous mobile hosts, allowing on-line and off-line access to data. We describe xmiddle using a collaborative e-shopping case study on mobile clients.

and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made.

This paper describes what we see as fundamental difficulties in both the pure ubiquitous computing and pure wearable computing paradigms when applied to context-aware applications. In particular, ubiquitous computing and smart room systems tend to have difficulties with privacy and personalization, while wearable systems have trouble with localized information, localized resource control, and resource management between multiple people. These difficulties are discussed, and a peer-to-peer network of wearable and ubiquitous computing components is proposed as a solution. This solution is demonstrated through several implemented applications.

Pervasive computing, with its focus on users and their tasks rather than on computing devices and technology, provides an attractive vision for the future of computing. But, while hardware and networking infrastructure to realize this vision are increasingly becoming a reality, precious few applications run in this infrastructure. We believe that this lack of applications can be attributed to three characteristics that are inadequately addressed by existing systems. First, devices are heterogeneous, ranging from wearable devices to conventional computers. Second, network connectivity often is limited and intermittent. And, third, interactions typically involve several autonomous administrative domains. In this paper, we introduce a system architecture that directly addresses these challenges. Our architecture is targeted at application developers and administrators, and it supports mobile computations, persistent storage, and resource discovery within a single, comprehensive framework....

This paper proposes a novel distributed service discovery protocol for Mobile Ad hoc Networks. The protocol is based on the concept of peer-to-peer caching of service advertisements and group-based intelligent forwarding of service requests. It does not require a service to register to a registry or lookup server. Services are described using an ontology based on the DARPA Agent Markup Language (DAML+OIL). We exploit the semantic class/subClass hierarchy of DAML to describe service groups and use this semantic information to selectively forward service requests to respective nodes. DAML-based service description helps us in achieving increased flexibility in service matching. We also present simulation results of our protocol and show that our protocol achieves increased efficiency in discovering services by efficiently utilizing bandwidth by controlling forwarding of service requests.

Pervasive computing provides an attractive vision for the future of computing. Computational power will be available everywhere. Mobile and stationary devices will dynamically connect and coordinate to seamlessly help users in accomplishing their tasks. However, for this vision to become a reality, developers must build applications that constantly adapt to a highly dynamic computing environment. To make the developers' task feasible, we introduce a system architecture for pervasive computing, called one.world . Our architecture provides an integrated and comprehensive framework for building pervasive applications. It includes a set of services, such as service discovery, checkpointing, migration, and replication, that help to structure applications and directly simplify the task of coping with constant change. We describe the design and implementation of our architecture and present the results of an evaluation, which includes two case studies.