Technological advances in semiconductor processing and design as well as wireless networking are leading us towards the vision of Pervasive Computing. We envision that in the (near) future, devices all around a person, either embedded as a part of smart spaces, or being carried by other people in the vicinity, will provide an array of services that she might want to use. Development of customized services by integrating and executing existing ones has received a lot of attention in the last few years with respect to wired, infrastrutcure based web-services. However, service discovery and composition in web-based environments is performed in a centralized manner with the help of a fixed entity. Moreover, wired infrastructure-based service discovery and composition architectures do not take into consideration factors arising from the possible mobility of the service providers. In this paper, we present a distributed, de-centralized and fault-tolerant design architecture for reactive service composition in pervasive environments. The design of the architecture is based on a peer-to-peer model. We introduce two reactive techniques for service composition in our design. We also present the Anamika system, an initial implementation of our design architecture. We present experiments to show the functioning of our design and implementation.

Abstract—The paper proposes a novel distributed service discovery protocol for pervasive environments. The protocol is based on the concepts of peer-to-peer caching of service advertisements and group-based intelligent forwarding of service requests. It does not require a service to be registered with a registry or lookup server. Services are described using the Web Ontology Language (OWL). We exploit the semantic class/subClass hierarchy of OWL to describe service groups and use this semantic information to selectively forward service requests. OWL-based service description also enables increased flexibility in service matching. We present simulation results that show that our protocol achieves increased efficiency in discovering services (compared to traditional broadcast-based mechanisms) by efficiently utilizing bandwidth via controlled forwarding of service requests.

A configurable and dynamically reconfigurable multipersonality middleware supports the discovery of services advertised on multiple platforms and achieves interoperability between heterogeneous discovery protocols. In pervasive computing environments, computer systems vanish into the background, providing users with relevant services and information anytime, anywhere. Without prior knowledge of the available resources or what method should be used to communicate with them, discovering the appropriate services is challenging. Many service discovery protocols (SDPs) address this task. Each is typically tailored for a specific environment type. For example, protocols for fixed infrastructure networks include SLP (Service Location Protocol), UPnP (Universal Plug and Play), and Jini, and protocols for adhoc networks include Allia, 1 GSD (Group-based Service Discovery), 2 and SSD (Scalable Service Discovery). 3 These protocols have a common purpose: to advertise and discover services. Nevertheless, they differ significantly in terms of, for example, service descriptions and directory architectures. So, finding services advertised using multiple protocols is an important challenge. Numerous middleware technologies for overcoming SDP heterogeneity have emerged. 4–8 However, these solutions are limited in scope. They tend to focus on fixed-infrastructure wired and wireless

Service discovery is an emerging field in the area of ubiquitous computing. There are various techniques and protocols (proposed or/and already implemented) particularly tailored to specific sets of objectives. This paper analyses the current state of the art and presents a taxonomy of service discovery protocols. Along with design issues, the diversity of solutions and open questions are systematically studied. 1

Location services are used in mobile ad hoc and hybrid networks either to locate the geographic position of a given node in the network or for locating a data item (content). One of the main usages of position location services is in location based routing algorithms. In particular, geographic routing protocols can route messages more efficiently to their destinations based on the destination node’s geographical position, which is provided by a location service. A content location service provides to the requesting node either the requested data itself or the identifier of the node that stores this data. Sometimes the position of the node that stores the data is also provided. Such data location services are useful for implementing content-sharing applications, cooperative caching, and publish subscribe systems. In this paper we present a taxonomy of location services and survey known techniques for constructing such a service in wireless ad hoc and hybrid networks.

Service discovery in Mobile Ad Hoc Networks is an essential process in order for these networks to be selfconfigurable. In this paper we argue that Service Discovery can be greatly enhanced in terms of efficiency (regarding service discoverability and energy consumption), by piggybacking service information in routing layer messages. Thus, a node requesting a service in addition to discovering that service, it is simultaneously informed of the route to the service provider.We extend the Zone Routing Protocol in order to encapsulate service information in its routing messages and through extensive simulations we prove the superiority of our routing layer-enhanced service discovery scheme against an application layer-based flooding scheme. I.

Abstract—Many ubiquitous computing applications may be context-sensitive due to the ambient environments, mobile devices, and other detectable factors. A context-sensitive middleware provides the necessary support to context-sensitive application objects to participate in spontaneous and ad hoc communications with other applications in remote devices whenever suitable contexts exist. A context-sensitive middleware can provide this support effectively if its communication subsystem, such as an Object Request Broker (ORB), can properly discover other objects in devices. This capability is usually known as object discovery protocol. An energy-efficient object discovery protocol is needed to help prolong a device’s battery life because many devices in ubiquitous computing environments are battery-powered and, thus, have limited energy sources. In this paper, an energy-efficient object discovery protocol, RKS, for context-sensitive middleware for ubiquitous computing is presented. RKS reduces energy consumption by reducing the amount of information that needs to be sent to remote devices to discover objects. A novel feature of RKS is that it advertises its server-objects’ availability only when it detects that these servers can be activated in the current context and when it finds that the neighbor devices have some potential clients that are willing to discover objects. Analytical comparisons of the energy-consumptions are given between RKS and two other protocols for object discovery in context-sensitive middleware. Furthermore, our experimental results, based on the implementations of these protocols and RKS on a context-sensitive middleware test bed, confirm our analytical results in that the RKS conserves more energy than the other two. Index Terms—Object discovery protocol, context-sensitive middleware, ubiquitous computing, mobile ad hoc networks, energy efficiency, reconfigurable context-sensitive middleware. æ 1

Abstract: A novel approach to performing context discovery in ad-hoc networks based on the use of attenuated Bloom filters is proposed in this paper. A Bloom filter is an efficient space-saving data structure to represent context information. Attenuated Bloom filters are used to advertise the availability of context information multiple hops away, and to guide queries to discover it. In order to investigate the performance of this approach, a model has been developed. This paper describes the model and its validat ion. From the results obtained with the model, using attenuated Bloom filters appear to be a very promising approach for context discovery in ad hoc networks. Compared to conventional solutions, the traffic load of our approach is an order of magnitude lower in practical situations.

Discovering the appropriate services in ad-hoc computing environments where a great number of devices and software components collaborate discreetly and provide numerous services is an important challenge. Service discovery protocols make it possible for participating nodes in a network to locate and advertise services with minimum user intervention. However, because it is not possible to predict at design time which protocols will be used to advertise services in a given context/ environment, it is now becoming clear that dynamic discovery mechanisms are required by mobile nodes to cope with the heterogeneity of discovery platforms. Existing adaptive mobile middleware solutions such as ReMMoC and INDISS have investigated this style of dynamic discovery. However, these have yet to consider the emerging suite of protocols for discovery in ad-hoc networks. In this paper we present a component-based service discovery framework for the development of an adaptive multi-personality service discovery middleware, which will operate in diverse environments e.g. fixed and ad-hoc networks. This supports a common architecture for individual discovery protocols to enhance configurability and re-configurability of the framework, and minimize resource usage through component reuse. Finally, to evaluate this framework we investigate the development of four existing ad-hoc service discovery protocols using our approach.

Distributed systems now encounter extreme heterogeneity in the form of diverse devices, network types etc., and also need to dynamically adapt to changing environmental conditions. Selfadaptive middleware is ideally situated to address these challenges. However, developing such software is a complex task. In this paper, we present the Gridkit self * approach to the engineering of reflective middleware; this embraces state of the art software engineering practices, and flexible dynamic adaptation mechanisms to better support system developers. Domain specific frameworks are modeled and developed to enhance configurability and reconfigurability. We evaluate this approach using case studies in the domains of service discovery and network overlays. These demonstrate the benefits of the approach in terms of aiding and simplifying the process of creating self-configuring and self-adaptive software.