A Lightweight Coordination Model and Middleware for Mobile Computing

Limone is a new coordination model and middleware that enables rapid application development for wireless ad hoc networks entailing logical mobility of agents and physical mobility of hosts. Designed to function in open environments, Limone performs automatic agent discovery but filters the results to define for each agent an individualized acquaintance list in accordance with run-time policies that are customizable by the application. This asymmetry among participants represents a new direction in coordination research and is dictated by the need to accommodate settings involving large numbers of agents and hosts that come and go freely. The coordination context is limited to the specific needs of the individual agent and its coordination activities are restricted to tuple spaces owned by peers present in the acquaintance list. Designed for wireless ad hoc networks, Limone tailors Linda-like primitives to address the challenges of mobile environments. This entails the elimination of remote blocking operations and the addition of timeouts to all distributed operations since disconnection with the affected agents may occur at any time. It also entails the addition of reactions that are triggered by the presence of information of interest on agents listed in the acquaintance list. Finally, to ensure performance and ease of deployment on small devices the granularity of atomic operations and the assumptions about the environment have been minimized. This paper introduces Limone, explains its key features, illustrates its usage, and explores its effectiveness as a software engineering tool

Active Coordination in Ad Hoc Networks

The increasing ubiquity of communicating mobile devices and vastly different mobile application needs have led to the emergence of middleware models for ad hoc networks that simplify application programming. One such system, EgoSpaces, addresses specific needs of individual applications, allowing them to define what data is included in their operating context using declarative specifications constraining properties of data, agents that own the data, hosts on which those agents are running, and attributes of the ad hoc network. In the resulting coordination model, application agents interact with a dynamically changing environment through a set of views, or custom defined projections of the set of data present in the surrounding ad hoc network. This paper builds on EgoSpaces by allowing agents to assign behaviors to their personal-ized views. Behaviors consist of actions that are automatically performed in response to specified changes in a view. Behaviors discussed in this paper encompass reactive programming, transparent data migration, automatic data duplication, and event capture. Formal semantic definitions and programming examples are given for each behavior

Secure Sharing of Tuple Spaces in Ad Hoc Settings

AbstractSecurity is emerging as a growing concern throughout the distributed computing community. Typical solutions entail specialized infrastructure support for authentication, encryption and access control. Mobile applications executing over ad hoc wireless networks present designers with a rather distinct set of security requirements. A totally open setting and limited resources call for lightweight and highly decentralized security solutions. In this paper we propose an approach that relies on extending an existing coordination middleware for mobility (Lime). The need to continue to offer a very simple model of coordination that assures rapid software development led to limiting extensions solely to password protected tuple spaces and per tuple access control. Password distribution and security are relegated to the application realm. Host level security is ensured by the middleware design and relies on standard support provided by the Java system. Secure interactions among agents across hosts are accomplished by careful exploitation of the interceptor pattern and the use of standard encryption. The paper explains the design strategy used to add security support in Lime and its implications for the development of mobile applications over ad hoc networks

Active Coordination in Ad Hoc Networks

Abstract. The increasing ubiquity of communicating mobile devices and vastly different mobile application needs have led to the emergence of middleware models for ad hoc networks that simplify application pro-gramming. One such system, EgoSpaces, addresses specific needs of indi-vidual applications, allowing them to define what data is included in their operating context using declarative specifications constraining properties of data, agents that own the data, hosts on which those agents are run-ning, and attributes of the ad hoc network. In the resulting coordination model, application agents interact with a dynamically changing environ-ment through a set of views, or custom defined projections of the set of data present in the surrounding ad hoc network. This paper builds on EgoSpaces by allowing agents to assign behaviors to their personal-ized views. Behaviors consist of actions that are automatically performed in response to specified changes in a view. Behaviors discussed in this paper encompass reactive programming, transparent data migration, au-tomatic data duplication, and event capture. Formal semantic definitions and programming examples are given for each behavior.

Simplifying Context-Aware Agent Coordination Using Context-Sensitive Data Structures

Context-aware computing, an emerging paradigm in which applications sense and adapt their behavior to changes in their operational environment, is key to developing dependable agent-based soft-ware systems for use in the often unpredictable settings of ad hoc net-works. However, designing an application agent which interacts with other agents to gather, maintain, and adapt to context can be a difficult undertaking in an open and continuously changing environment, even for a seasoned programmer. Our goal is to simplify the programming task by hiding the details of agent coordination from the programmer, allowing one to quickly and reliably produce a context-aware application agent for use in large-scale ad hoc networks. With this goal in mind, we introduce a novel abstraction called context-sensitive data structures (CSDS). The programmer interacts with the CSDS through a familiar programming interface, without direct knowledge of the context gathering and maintenance tasks that occur behind the scenes. In this paper, we define a model of context-sensitive data structures, and we identify key requirements and issues associated with building an infrastructure to support the development of context-sensitive data structures

Achieving Coordination Through Dynamic Construction of Open Workflows ** PLEASE SEE WUCSE-2009-14 **

Workflows, widely used on the Internet today, typically consist of a graph-like structure that defines the orchestration rules for executing a set of tasks, each of which is matched at run-rime to a corresponding service. The graph is static, specialized directories enable the discovery of services, and the wired infrastructure supports routing of results among tasks. In this paper we introduce a radically new paradigm for workflow construction and execution called open workflow. It is motivated by the growing reliance on wireless ad hoc networks in settings such as emergency response, field hospitals, and military operations. Open workflows facilitate goal-directed coordination among physically mobile agents (people and host devices) that form a transient community over an ad hoc wireless network. The quintessential feature of the open workflow paradigm is the ability to construct a custom context-specific workflow specification on the fly in response to unpredictable and evolving circumstances by exploiting the knowhow and services available within a given spatiotemporal context. This paper introduces the open workflow approach and explores the technical challenges (algorithms and architecture) associated with its first practical realization

Blackboard Rules for Coordinating Context-aware Applications in Mobile Ad Hoc Networks

Thanks to improvements in wireless communication technologies and increasing computing power in hand-held devices, mobile ad hoc networks are becoming an ever-more present reality. Coordination languages are expected to become important means in supporting this type of interaction. To this extent we argue the interest of the Bach coordination language as a middleware that can handle and react to context changes as well as cope with unpredictable physical interruptions that occur in opportunistic network connections. More concretely, our proposal is based on blackboard rules that model declaratively the actions to be taken once the blackboard content reaches a predefined state, but also that manage the engagement and disengagement of hosts and transient sharing of blackboards. The idea of reactiveness has already been introduced in previous work, but as will be appreciated by the reader, this article presents a new perspective, more focused on a declarative setting.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432

Coordination of Mobile Mules via Facility Location Strategies

In this paper, we study the problem of wireless sensor network (WSN) maintenance using mobile entities called mules. The mules are deployed in the area of the WSN in such a way that would minimize the time it takes them to reach a failed sensor and fix it. The mules must constantly optimize their collective deployment to account for occupied mules. The objective is to define the optimal deployment and task allocation strategy for the mules, so that the sensors' downtime and the mules' traveling distance are minimized. Our solutions are inspired by research in the field of computational geometry and the design of our algorithms is based on state of the art approximation algorithms for the classical problem of facility location. Our empirical results demonstrate how cooperation enhances the team's performance, and indicate that a combination of k-Median based deployment with closest-available task allocation provides the best results in terms of minimizing the sensors' downtime but is inefficient in terms of the mules' travel distance. A k-Centroid based deployment produces good results in both criteria.Comment: 12 pages, 6 figures, conferenc