An event service supporting autonomic management of ubiquitous systems for e-health

An event system suitable for very simple devices corresponding to a body area network for monitoring patients is presented. Event systems can be used both for self-management of the components as well as indicating alarms relating to patient health state. Traditional event systems emphasise scalability and complex event dissemination for internet based systems, whereas we are considering ubiquitous systems with wireless communication and mobile nodes which may join or leave the system over time intervals of minutes. Issues such as persistent delivery are also important. We describe the design, prototype implementation, and performance characteristics of an event system architecture targeted at this application domain

Towards verifying correctness of wireless sensor network applications using Insense and Spin

The design and implementation of wireless sensor network applications often require domain experts, who may lack expertise in software engineering, to produce resource-constrained, concurrent, real-time software without the support of high-level software engineering facilities. The Insense language aims to address this mismatch by allowing the complexities of synchronisation, memory management and event-driven programming to be borne by the language implementation rather than by the programmer. The main contribution of this paper is all initial step towards verifying the correctness of WSN applications with a focus on concurrency. We model part of the synchronisation mechanism of the Insense language implementation using Promela constructs and verify its correctness using SPIN. We demonstrate how a previously published version of the mechanism is shown to be incorrect by SPIN, and give complete verification results for the revised mechanism.Preprin

Type-Based Publish/Subscribe

This paper presents type-based publish/subscribe, a new variant of the publish/subscribe paradigm. Producers publish message objects on a communication bus, and consumers subscribe to the bus by specifying the types of the objects they are interested in. Message objects are considered as first class citizens and are classified by their types, instead of arbitrarily fixed topics. By reusing the type scheme of the language to classify message objects, type-based publish/subscribe avoids any unnatural subscription scheme and provides for a seamless integration of a publish/subscribe middleware with the programming language. Type-based publish/subscribe has several quantifiable advantages over other publish/subscribe variants. In particular, the knowledge of the type of message objects enforces performance optimizations when combined with dynamic filters for content-based subscription. %from dynamically defined requirements. Our type-based publish/subscribe prototype is based on Distributed Asynchronous Collections (DACs), programming abstractions for publish/subscribe interaction. They are implemented using GJ, an extended Java compiler adding genericity to the Java language, and enable the expression of safely typed distributed interaction without requiring any generation of typed proxies

Hera-JVM: a runtime system for heterogeneous multi-core architectures

Heterogeneous multi-core processors, such as the IBM Cell processor, can deliver high performance. However, these processors are notoriously difficult to program: different cores support different instruction set architectures, and the processor as a whole does not provide coherence between the different cores ’ local memories. We present Hera-JVM, an implementation of the Java Virtual Machine which operates over the Cell processor, thereby making this platforms more readily accessible to mainstream developers. Hera-JVM supports the full Java language; threads from an unmodified Java application can be simultaneously executed on both the main PowerPCbased core and on the additional SPE accelerator cores. Migration of threads between these cores is transparent from the point of view of the application, requiring no modification to Java source code or bytecode. Hera-JVM supports the existing Java Memory Model, even though the underlying hardware does not provide cache coherence between the different core types. We examine Hera-JVM’s performance under a series of real-world Java benchmarks from the SpecJVM, Java Grande and Dacapo benchmark suites. These benchmarks show a wide variation in relative performance on the different core types of the Cell processor, depending upon the nature of their workload. Execution of these benchmarks on Hera-JVM can achieve speedups of up to 2.25x by using one of the Cell processor’s SPE accelerator cores, compared to execution on the main PowerPC-based core. When all six SPE cores are exploited, parallel workloads can achieve speedups of up to 13x compared to execution on the single PowerPC core

Effective multicast

programming in large scale distributed system

Effective Multicast Programming in Large Scale Distributed Systems ∗

Many distributed applications have a strong requirement for efficient dissemination of large amounts of information to widely spread consumers in large networks. These include applications in e-commerce and telecommunication. Publish/subscribe is considered one of the most important interaction styles to model communication at large scale. Producers publish information for a topic and consumers subscribe to the topics they wish to be informed of. The decoupling of producers and consumers in time, space, and flow makes the publish/subscribe paradigm very attractive for large scale distribution, especially in environments like the Internet. This paper describes the architecture and implementation of DACE (Distributed Asynchronous Computing Environment), a framework for publish/subscribe communication based on an object-oriented programming abstraction in the form of Distributed Asynchronous Collection (DAC). DACs capture the different variations of publish/subscribe, without blurring their respective advantages. The architecture we present is tolerant to network partitions and crash failures. The underlying model is based on the notion of Topic Membership: a weak membership for the parties involved in a topic. We present how Topic Membership enables the realization of a robust and efficient reliable multicast for large scale. The protocol ensures that, inside a topic, even a subscriber that is temporarily partitioned away eventually receives a published message