David Linner

Modeling and Controlling Dynamic Service Compositions

Service-oriented computing paradigms have considerably enhanced support for dynamic in modern computing environments by providing loosely coupled interactions between components. The key attainment is the ability to perform a late binding of service compositions, i.e., an allocation of actual services to service place holders during run-time. However, this attainment is limited to the binding of services and cannot operate on the service composition plans itself. Moreover, many service composition representations do not consider the realtime behavior of single services, failing to address a key need of service compositions within dynamic environments that are characterized by a high node mobility. Within this paper, we introduce a service composition model based on a bipartite graph representation that enables the rapid modification of already existing service composition plans. Here, the workflow within a service composition is modeled with a timed automaton while a labeled digraph ensures the correct flow of data between the single services.

A genetic algorithm for the adaptation of service compositions

The view on applications in large-scale open systems shifted to a service-oriented perspective, where each functional feature forming an application is regarded as service. The services which constitute an application can be physically spread over different network nodes and can be even provided by different administrative entities. According to the vision of the BIONETS project we are additionally facing a dynamically changing computing environment, which entails a dynamically changing set of available services. We investigate how service compositions, on which novel applications are based on, can flexibly be adapted to the changing conditions in the computing environment, while going beyond late-binding mechanisms. We apply methods of genetic programming to modify the structures describing service compositions to find compensation for types of services no longer available to applications. In this paper, we describe the current state of our efforts on complex algorithms for service composition transformation, based on the application of genetic operators to graph based service composition representations.

Request-driven Service Provisioning

Heterogeneous smart and mobile devices increasingly form a pervasive computing environment. Service oriented architecture (SOA) provides a unified view on the resources and services of those environments to make them easily available for applications. However, variations in the reliability and the availability of these services result in special requirements for the interactions of service providers and service requesters. In this paper we propose a SOA approach that is based on temporally and spatially uncoupled interactions, and supports a loose coupling in the terminology of exchanged data. For that purpose we define a service model as well as an interaction model for request-driven service provisioning and present an approach for the implementation of these models

BIONETS architecture: from networks to SerWorks

This paper presents the networking framework as conceived within the European project BIONETS. The case for such a framework comes from the idea of a ldquoDisappearing Networkrdquo paradigm. In the disappearing network, the network ceases to exist as an independent entity and becomes an appendix of the distributed services running on user devices. The overall BIONETS system exploits the presence of embedded devices to provide context-awareness and leverages peer-to-peer interactions among mobile devices in order to ensure system-wide dissemination of data and services. Some of the current networking solutions developed within the project are also presented, highlighting the use of bio-inspired techniques and tools. The paper presents then a first version of the SerWorks architecture, which takes a unifying view on networks and services. In SerWorks, the network becomes a set of particular services, aimed at general connectivity purposes, which can be created and modified at runtime in order to accommodate for specific system conditions and higher-level constraints.

Loosely Coupled Service Provisioning in Dynamic Computing Environments

Smart environments and mobile computing systems increasingly converge, resulting in the emergence of pervasive computing environments. This development brings up new challenges that pertain to the variable availability and different mobility of heterogeneous services. Existing service interaction patterns in the area of service-oriented architecture (SOA) do not sufficiently address the changed requirements in those highly dynamic environments, which makes new approaches necessary. Our request-driven SOA approach for service provisioning described in this paper spatially, temporally, and semantically decouples interactions of service providers and requesters making it possible to cope with the unreliable and changing character of pervasive computing environments. We incorporated the developed ideas and models into a prototypical implementation to prove our concept.

Bio-inspired context gathering in loosely coupled computing environments

Context-awareness is a key requirement of human-centric computing systems. Applications may ease user interaction or even anticipate the behavior of the user when utilizing information about the current context. The pervasive provision of context data represents a major challenge in this scope. For that reason we introduce an approach for gathering, disseminating, and interpreting context data in dynamic, highly distributed systems, which are mostly disconnected from central networking infrastructures. On the one hand we describe architectural consideration addressing functional elements and their organization in the computing environment. On the other hand we incorporate a model for request-driven context gathering and a biologically-inspired approach for weighting, storing and forwarding context data. The conceptual considerations are complemented with a description of our first efforts in realizing our approach on top of a peer-to-peer framework

Autonomous Context Data Dissemination in Heterogeneous and Dynamic Environments

The intelligent dissemination of context information to enable context-aware applications is a topic often discussed in current research. However, related approaches are not able to cope with the unknown and dynamically changing nature often found in ad-hoc peer-to-peer environments. In this paper, we propose a flexible means of gathering, interpreting, and providing context information in a distributed manner. For this purpose, we describe a request-driven model for the interaction of context providers and requesters. We incorporate a bio- inspired pheromone-based approach of intelligently storing and disseminating information based on the data really requested and needed. Semantic Web technology is utilized to obtain a loosely coupled interaction pattern and an adaptable representation of context information. Thus, desired information can be accessed by external applications and services in a flexible and transparent manner.

BIO-INSPIRED PROCESSING AND PROPAGATION OF SEMANTICS IN LOOSELY COUPLED COMPUTING ENVIRONMENTS

Human-centric computing has grown to be the major influence in todays computing research. Due to demand from industry and even lawmakers for easy-to-use computer systems, the user is now regarded as being the center of a ubiquitously available environment that supports the execution of task and anticipates user actions. This environment allows for the establishment of completely new ways for the delivery of legacy services and represents an opportunity for the introduction of a new type of services, addressing the user-focused service consumption. As a cause of this shift, the increasing saturation of everyday environments with computing devices can be identified. This saturation implies a numerical growth of computing systems and entails an increasing complexity, which negatively influences maintainability and manageability. Moreover, the shortcomings caused by the mobility of system elements, a common trait of human-centric environments, require consideration about the reliability of cooperative actions. In this paper, we present an approach that copes with complexity and dynamic while making service-oriented systems autonomous by the use of bio-inspired concepts. In particular, the aim is to make service architectures environment-aware. Thus, service architectures are supposed to adapt autonomously to their current environment like biological species do to survive. This approach requires services to obtain knowledge about characteristics and state of the environment through gathering semantically enhanced information about the context of the computing environment, which is intended to help in forming a virtual counterpart of the real world as reference for service adaptation. For this purpose, we illustrate the architecture for context provisioning in highly dynamic computing environments. As base for this architecture a middleware is introduced utilizing a loosely coupled interaction model. Moreover, a pheromone-based concept is outlined to optimize the dissemination of context data in the absence of adequate context sources.

SmartWare: framework for autonomic application services

The combination of mobile and embedded computing devices holds potential for a novel landscape of application and services in the direct surrounding of the user. The realization of such a landscape requires solutions to cope with the volatile nature of the environment composition, the absence of central management infrastructure, and the heterogeneity of resources. To unburden developers of application services from searching these solutions themselves, we started developing a generic software framework called SmartWare. SmartWare is a collection of principles and tools that are intended to simplify and accelerate the development of application services at the edge of the Internet and beyond. In this paper we describe the features of SmartWare, a prototype implementation and a test application we realized with the framework prototype.

Automatic routing of semantic SIP messages in IMS

The IP multimedia subsystem (IMS) is considered as a valid possibility to tackle the seamless provision of multimedia services in both packet switched and circuit switched networks. The session initiation protocol (SIP) is applied as a protocol for signaling, but is not yet used to fully exploit the potential of dynamic and context-aware service provision. In this paper we present a method to semantically enhance SIP. Tailored to this method, a novel kind of proxy is introduced to enable the automatic interpretation of user requests in a context-aware manner. The decoupling of service request and response in terms of semantic addressing facilitates the immediate publication of new services in IMS and eases the creation of user requests.