Introduction to the special section on dependable network computing

Dependable network computing is becoming a key part of our daily economic and social life. Every day, millions of users and businesses are utilizing the Internet infrastructure for real-time electronic commerce transactions, scheduling important events, and building relationships. While network traffic and the number of users are rapidly growing, the mean-time between failures (MTTF) is surprisingly short; according to recent studies, in the majority of Internet backbone paths, the MTTF is 28 days. This leads to a strong requirement for highly dependable networks, servers, and software systems. The challenge is to build interconnected systems, based on available technology, that are inexpensive, accessible, scalable, and dependable. This special section provides insights into a number of these exciting challenges

Enhancing Planning-Based Adaptation Middleware with Support for Dependability: a Case Study

Recent evolutions of mobile devices have opened up for new opportunities for building advanced mobile applications. In particular, these applications are capable of discovering and exploiting software and hardware resources that are made available in their environment. A possible approach for supporting these ubiquitous interactions consists in adapting the mobile application to reflect the functionalities that are provided by the environment. However, these approaches often fail in offering a sufficient degree of resilience to potential device, network, and software failures, which are particularly frequent in ubiquitous environments. Therefore, the contribution of this paper is to integrate the dependability concern in the process of mobile applications adaptation. In particular, we propose to reflect dependability mechanisms as alternative configurations for a given application. This reflection allows the planning-based adaptation middleware to automatically decide, based on contextual information, to enable the support for dependability or not

How Governance Regimes Shape the Implementation of Water Reuse Schemes

The governance dimensions of water reuse scheme development and operation, such as policies and regulatory frameworks, and public involvement and stakeholder collaboration, can serve to both facilitate and constrain wider adoption of water reuse practices. This paper explores the significance and underlying structure of the key governance challenges facing the water reuse sector in Europe. It presents empirical evidence from interviews and focus group sessions conducted at four water reuse schemes: an indirect potable reuse scheme at Torreele (Belgium), the urban reuse of treated municipal wastewater at the London Olympic Park (United Kingdom) and at Sabadell (Spain), and the reuse of agro-industrial effluent for irrigation at Capitanata (Italy). The findings underscore the importance of clarity in policy arrangements around water reuse, as well as of the financial competitiveness of reuse projects compared to alternative water supply options. Operators of water reuse schemes expressed a preference for water quality standards, which focus on appropriateness for use rather than over-emphasise the waters’ origin so that unnecessary treatment and costs can be avoided. Positive public support was widely acknowledged as an important factor in the success or failure of water reuse schemes. We conclude that constructive institutional relationships underpin many of the challenges faced by reuse scheme operators and that greater emphasis should be given to building confidence and gaining trust in water service providers through early identification of how governance regimes shape the viability of new scheme

Automatic performance optimisation of component-based enterprise systems via redundancy

Component technologies, such as J2EE and .NET have been extensively adopted for building complex enterprise applications. These technologies help address complex functionality and flexibility problems and reduce development and maintenance costs. Nonetheless, current component technologies provide little support for predicting and controlling the emerging performance of software systems that are assembled from distinct components. Static component testing and tuning procedures provide insufficient performance guarantees for components deployed and run in diverse assemblies, under unpredictable workloads and on different platforms. Often, there is no single component implementation or deployment configuration that can yield optimal performance in all possible conditions under which a component may run. Manually optimising and adapting complex applications to changes in their running environment is a costly and error-prone management task. The thesis presents a solution for automatically optimising the performance of component-based enterprise systems. The proposed approach is based on the alternate usage of multiple component variants with equivalent functional characteristics, each one optimized for a different execution environment. A management framework automatically administers the available redundant variants and adapts the system to external changes. The framework uses runtime monitoring data to detect performance anomalies and significant variations in the application's execution environment. It automatically adapts the application so as to use the optimal component configuration under the current running conditions. An automatic clustering mechanism analyses monitoring data and infers information on the components' performance characteristics. System administrators use decision policies to state high-level performance goals and configure system management processes. A framework prototype has been implemented and tested for automatically managing a J2EE application. Obtained results prove the framework's capability to successfully manage a software system without human intervention. The management overhead induced during normal system execution and through management operations indicate the framework's feasibility

Spartan Daily, November 21, 1994

Volume 103, Issue 57https://scholarworks.sjsu.edu/spartandaily/8627/thumbnail.jp

Design and Performance of a Fault-Tolerant Real-Time CORBA Event Service

Developing distributed real-time and embedded (DRE)systems in which multiple quality-of-service (QoS) dimen-sions must be managed is an important and challenging R&D problem. This paper makes three contributions to re-search on multi-dimensional QoS for DRE systems. First, itdescribes the design and implementation of a fault-tolerantreal-time CORBA event service for The ACE ORB (TAO).Second, it describes our enhancements and extensions tofeatures in TAO, to integrate real-time and fault toleranceproperties. Third, it presents an empirical evaluation ofour approach. Our results show that with some refinements,real-time and fault-tolerance features can be integrated ef-fectively and efficiently in a CORBA event service