Early Aspects work at Lancaster in the AOSD Europe project

Abstract Data Type

Abstract: In this paper we introduce the concept of Distributed Abstract Data Type (DADT), a new programming model simplifying the development of distributed, context-aware applications. A DADT instance logically encapsulates a collection of ADT instances distributed throughout the system. DADT operationsspecify the semantics of access to this distributed state by using dedicated programming constructs. The scope of these operations can be restricted using DADT views, i.e., projections over the target ADT instances, defined declaratively and dynamically based on ADT properties. Interestingly, DADT constructs can be used to deal not only with application data, but also with the space where it resides. This leads to a uniform treatment of the data and space concerns, simplifying the development of context-aware applications and providing the programmer with considerable flexibility and expressive power.We argue that DADTs are amenableto incorporation in existing object-oriented programming languages, as demonstrated by our prototype implementation.

Paper : http://www.inf.unisi.ch/faculty/murphy/Papers/dadt.pdf

Abstract:   Distributed event routing has emerged as a key technology for achieving  scalable information dissemination. In particular it has been used as preferential communication backbone within publish/subscribe communication system. Its aim is to reduce the network and computational overhead per event diffusion to a set (possibly large) of interested recipients. This paper introduces an unifying framework, namely a publish/subscribe architecture, that points out the functional decomposition between event-based routing layer, the overlay infrastructure layer and the network protocols layer. Hence the paper, firstly, surveys current algorithms for event based routing and possible overlay infrastructures in wired and mobile systems and, secondly, it discusses how and when single solutions at each level can be combined in the publish/subscribe architecture. Finally the paper positions existing publish/subscribe.

Abstract: "Overlay topology plays an important role in P2P systems. Topology serves as a basis for achieving functions such as routing, searching and information dissemination, and it has a major impact on their efficiency, cost and robustness. Furthermore, the solution to problems such as sorting and clustering of nodes can also be interpreted as a topology. In this paper we propose a generic protocol, T-Man, for constructing and maintaining a large class of topologies. In the proposed framework, a topology is defined with the help of a ranking function. The nodes participating in the protocol can use this ranking function to order any set of other nodes according to preference for choosing them as a neighbor. This simple abstraction makes it possible to control the self-organization process of topologies in a straightforward, intuitive and flexible manner. At the same time, the T-Man protocol involves only local communication to increase the quality of the current set of neighbors of each node. We show that this bottom-up approach results in fast convergence and high robustness in dynamic environments. The protocol can be applied as a standalone solution as well as a component for recovery or bootstrapping of other protocols."

Abstract: This paper presents a middleware framework to support the development of context-aware adaptive communication protocols, that can be reconfigured according not only to the local context, but also to the context of the remaining remote participants. The advantages of the framework are illustrated by using the concrete example of an adaptive group communication protocol. The protocol supports a distributed chat application that can be executed in both fixed PCs and mobile devices.

Abstract :Distribution-related concerns, such as data replication, often crosscut the business code of a distributed application. Currently such crosscutting concerns are frequently realized on top of distributed frameworks, such as EJBs, and initial AO support for the modularization of such crosscutting concerns, e.g., JBoss AOP and Spring AOP, has been proposed. Based on an investigation of the implementation of replicated caches using JBoss Cache, we motivate that crosscutting concerns of distributed applications benefit from an aspect language for explicit distributed programming. We propose AWED, a new aspect language with explicit distributed programming mechanisms, which provides three contributions. First, remote pointcut constructors which are more general than those of previous related approaches, in particular, supporting remote sequences. Second, a notion of distributed advice with support for asynchronous and synchronous execution. Third, a notion of distributed aspects including models for the deployment, instantiation and state sharing of aspects. We show several concrete examples how AWED can be used to modularly implement and extend replicated cache implementations. Finally, we present a prototype implementation of AWED, which we have realized by extending JAsCo, a system providing dynamic aspects for Java.

Service Discovery in Highly Heterogeneous Mobile Environments

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Abstract: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. Furthermore, mobile nodes are characterised by limited resources, so this problem must be tackled in an efficient manner. Existing adaptive mobile middleware solutions such as ReMMoC and INDISS have investigated this style of dynamic discovery. However, significant development effort is required for both systems i.e. components or translator development in order to integrate new protocol implementations. In this paper we present a component-based service discovery framework for the development of an adaptive multi-personality service discovery middleware. This supports a common architecture for individual discovery protocols to enhance configurability and reconfigurability of the framework, and minimise resource usage through component re-use. Finally, we evaluate this framework by investigating the development of four existing discovery protocols using our approach.

Generation of Reflective Middleware Families

Abstract: To develop models for reflective middleware families and transform them, applying generative techniques, into consistent sets of middleware configurations (families)

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Efficient Exploration of Service-Oriented Architectures using Aspects

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Abstract: An important step in the development of large-scale distributed, reactive systems is the design of architectures that effectively support the systems’ purposes. Early prototypes help to decide upon the most effective architecture for a given situation. Questions to answer include the boundaries of components, communication topologies and of replication. It is desirable to evaluate and compare architectures for functionality and quality attributes before implement ing or changing the whole system. Often, the effort required is prohibitive. In this paper we present an approach to efficiently create prototypes for service-oriented architectures using aspect-oriented programming techniques. We explain a procedure for transforming interaction based software specifications into AspectJ programs. We show how to map the same set of interaction scenarios to different candidate architectures. This significantly reduces the effort required to explore architectural alternatives. We explain and evaluate our approach using the Center TRACON Automation System as a running example

Integrating security policies via container portable interceptors

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Abstract.In the past, it was very common to develop middleware without consideration of security from the very beginning. To integrate security, the middleware that should be protected has to provide appropriate hooks and interfaces, and has to meet the requirements of security. In most cases it is not possible to develop a new, secure middleware from scratch. It is only possible to make minor modification to existing systems. In this paper we describe the successful integration of a CORBA Component based middleware and a policy management framework for the definition, management and enforcement of security policies. Integration is achieved by defining Container Portable Interceptors and QoS Enablers which provide the necessary hooks for interception and provision of context interfaces to integrate the security framework.

Abstract.This talk will provide an overview of the P2P ARCHITECT project, which focused on supporting software developing organisations in building dependable P2P software systems. As part of this project Lancaster developed DISCOS, a tool supported design methodology that encourages the developer to consider dependability and P2P issues throughout the development life cycle. This talk will also provide a brief overview of PEPERS, a new project that builds on our previous work and seeks to design, implement and validate a reliable platform with high-level support for the design, development and operational deployment of secure mobile peer-to-peer applications.

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Abstract.The development of distributed systems software is becoming increasingly complex. Aspect-oriented middleware (AOM) platforms aim to ease this complexity by allowing otherwise crosscutting concerns to be modularised, promoting understandability, evolvability and reusability.However, AOM platforms are becoming more widespread, diverse and also more complex. In this report we present a reference architecture for aspect-oriented middleware. The reference architecture provides a common reference point for the creation of key concerns which can then be mapped to a particular AOM platform. Additionally, the reference architecture facilitates the creation of new AOM platforms themselves.

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Abstract.The miniaturization of hardware components has lead to the development of Wireless Sensor Networks (WSN) and networked-applications over them. Meanwhile, middleware systems have also been proposed in order to both facilitating the development of these applications and providing common application services. The development of middleware for sensor networks, however, places new challenges to middleware developers due to the low availability of resources and processing capacity of the sensor nodes. In this context, this paper presents a middleware for WSN named Mires. Mires incorporates characteristics of message-oriented middleware by allowing applications communicate in a publish/subscribe way. In order to illustrate the proposed middleware, we implement an aggregation middleware service for an environment-monitoring application.

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Abstract.The need for adaptability in software is growing, driven in part by the emergence of pervasive and autonomic computing. In many cases, it is desirable to enhance existing programs with adaptive behavior, enabling them to execute effectively in dynamic environments. In this paper, we propose a general programming model called transparent shaping to enable dynamic adaptation in existing programs. We describe an approach to implementing transparent shaping that combines four key software development techniques: aspect-oriented programming to realize separation of concerns at development time, behavioral reflection to support software reconfiguration at run time, component-based design to facilitate independent development and deployment of adaptive code, and adaptive middleware to encapsulate the adaptive functionality. After presenting the general model, we discuss two specific realizations of transparent shaping that we have developed and used to create adaptable applications from existing programs.

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Abstract.The emergence of Grid computing has accentuated the need of an adaptable, scalable and extensible resource management system. In this paper we introduce GridARM system which renders the boundaries of resource brokerage, virtual organization wide authorization and advanced reservation, and represents a scalable and adaptive Grid resource management as a middleware infrastructure. The GridARM system provides mechanisms for Grid resource discovery, selection and allocation along with resource requestor and provider interaction. Experiments are presented that demonstrate the effectiveness of our approach.

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