Jean-Guy Schneider

Components, Scripts and Glue

Experience has shown us that object-oriented technology alone is not enough to guarantee that the systems we develop will be flexible and adaptable. Even “welldesigned” object-oriented software may be difficult to understand and adapt to new requirements. We propose a conceptual framework that will help yield more flexible object-oriented systems by encouraging explicit separation of computational and compositional elements. We distinguish between componentsthat adhere to an architectural style, scripts that specify compositions, and glue that may be needed to adapt components’ interfaces and contracts. We also discuss a prototype of an experimental composition language called P ICCOLA that attempts to combine proven ideas from scripting languages, coordination models and languages, glue techniques, and architectural specification.

A Survey of Policy-Based Management Approaches for Service Oriented Systems

Policy based management in service oriented architecture (SOA) allows organizations to apply rules and regulations on their business processes. Policy has long been employed in the management of traditional distributed systems and many policy frameworks have been proposed. However, SOA differs in several aspects to traditional systems thus there is a unique set of requirements for an effective SOA policy system. In this paper, we evaluate five popular policy frameworks which are IETF, Ponder, KAoS, Rei and WS-policy against a number of general and SOA-specific criteria to identify what features of these existing systems can be adopted for SOA and what are not. We then, based on their feature sets, discuss the applicability of the frameworks for SOA management.

Quality-Driven Business Policy Specification and Refinement for Service-Oriented Systems

Enterprise software systems play an essential role in an organizations business operation. Many business rules and regulations governing an organizations operation can be translated into quality requirements of the relevant software systems, such as security, availability, and manageability. For systems implemented using Web Services , the specification and management of these qualities in the form of Web Service policies are often complicated and difficult to be aligned with the initial business requirements. In this paper, we introduce the Hope (High-Level Objective-based Policy for Enterprises) framework that supports, in a systematic manner, the specification of quality-oriented policies at the business level and their refinement into policies at the system/service level. Quality-oriented business requirements are expressed in Hope as quality objectives applied to business entities and further refined or translated into system-level WS-Policy statements. The refinement relies on an application-specific business entity model and application-independent domain quality models. We demonstrate the approach with a case study involving policy specification and refinement in the security domain.

An energy consumption model and analysis tool for cloud computing environments

Cloud computing delivers computing as a utility to users worldwide. A consequence of this model is that cloud data centres have high deployment and operational costs, as well as significant carbon footprints for the environment. We need to develop Green Cloud Computing (GCC) solutions that reduce these deployment and operational costs and thus save energy and reduce adverse environmental impacts. In order to achieve this objective, a thorough understanding of the energy consumption patterns in complex Cloud environments is needed. We present a new energy consumption model and associated analysis tool for Cloud computing environments. We measure energy consumption in Cloud environments based on different runtime tasks. Empirical analysis of the correlation of energy consumption and Cloud data and computational tasks, as well as system performance, will be investigated based on our energy consumption model and analysis tool. Our research results can be integrated into Cloud systems to monitor energy consumption and support static or dynamic system-level optimisation.

Automated analysis of performance and energy consumption for cloud applications

In cloud environments, IT solutions are delivered to users via shared infrastructure. One consequence of this model is that large cloud data centres consume large amounts of energy and produce significant carbon footprints. A key objective of cloud providers is thus to develop resource provisioning and management solutions at minimum energy consumption while still guaranteeing Service Level Agreements (SLAs). However, a thorough understanding of both system performance and energy consumption patterns in complex cloud systems is imperative to achieve a balance of energy efficiency and acceptable performance. In this paper, we present StressCloud, a performance and energy consumption analysis tool for cloud systems. StressCloud can automatically generate load tests and profile system performance and energy consumption data. Using StressCloud, we have conducted extensive experiments to profile and analyse system performance and energy consumption with different types and mixes of runtime tasks. We collected fine-grained energy consumption and performance data with different resource allocation strategies, system configurations and workloads. The experimental results show the correlation coefficients of energy consumption, system resource allocation strategies and workload, as well as the performance of the cloud applications. Our results can be used to guide the design and deployment of cloud applications to balance energy and performance requirements.

Experimental analysis of task-based energy consumption in cloud computing systems

Cloud computing delivers IT solutions as a utility to users. One consequence of this model is that large cloud data centres consume large amounts of energy and produce significant carbon footprints. A common objective of cloud providers is to develop resource provisioning and management solutions that minimise energy consumption while guaranteeing Service Level Agreements (SLAs). In order to achieve this objective, a thorough understanding of energy consumption patterns in complex cloud systems is imperative. We have developed an energy consumption model for cloud computing systems. To operationalise this model, we have conducted extensive experiments to profile the energy consumption in cloud computing systems based on three types of tasks: computation-intensive, data-intensive and communication-intensive tasks. We collected fine-grained energy consumption and performance data with varying system configurations and workloads. Our experimental results show the correlation coefficients of energy consumption, system configuration and workload, as well as system performance in cloud systems. These results can be used for designing energy consumption monitors, and static or dynamic system-level energy consumption optimisation strategies for green cloud computing systems.

A preliminary analysis of vocabulary in mobile app user reviews

Online software distribution channels such as Apple Inc.s App Store and Google Inc.s Google Play provide a platform for third-party app distribution. These online stores feature a public review system, allowing users to express opinions regarding purchased apps. These reviews can influence product-purchasing decisions via polarised sentiment (1 to 5 stars) and user expressed opinion. For developers, reviews are a user-facing crowd-sourced indicator of app quality. Hence, high ratings and positive reviews affect the viability of an apps commercial feasibility. However, it is less clear what information is contained within these reviews, and more importantly, if an analysis of these reviews can inform developers of design priorities as opposed to just influencing purchasing decisions. We analysed 8.7 million reviews from 17,330 apps on the App Store and found that the most frequently used words in user reviews lean toward expressions of sentiment despite employment of only approximately 37% of the words within the English language dictionary. Furthermore, the range of words used to express negative opinions is significantly higher than when positive sentiments are expressed.

Detecting structural changes in object oriented software systems

It is an increasingly accepted fact that software development is a non-linear activity with inherently feedback driven processes. In such a development environment, however, it is important that major structural changes in the design and/or architecture of a software system under development are introduced with care and documented accordingly. In order to give developers appropriate tools that can identify such changes, we need to have a good understanding how software systems evolve over time so that evolutionary anomalies can be automatically detected. In this paper, we present recurring high-level structural and evolutionary patterns that we have observed in a number of public-domain object-oriented software systems and define a simple predictive model that can aid developers in detecting structural changes and as a consequence, improve the underlying development processes.

Formalizing Composable Software Systems — A Research Agenda

Flexibility is achieved in open systems by adopting software architectures that allow software components to be easily plugged in, adapted and exchanged. But open systems are generally concurrent, distributed and heterogeneous in addition to being adaptable. Ad hoc approaches to specifying component frameworks can lead to unexpected semantic conflicts. We propose, instead, to develop a rigorous foundation for composable software systems by a series of experiments in modelling concurrent and object-based software abstractions as composable, communicating processes. Eventually we hope to identify and realize the most useful compositional idioms as a composition language for open systems specification.

Partitioning of Java applications to support dynamic updates

The requirement for 24/7 availability of distributed applications complicates their maintenance and evolution as shutting down such applications to perform updates may not be an acceptable solution. Therefore, there is a need to be able to update these applications dynamically, i.e. without shutting them down. Current solutions for building dynamically updatable Java applications require that applications either are prepared for updates from the outset, comply with a specific framework, or are executed in a modified virtual machine. In this work, we present a novel approach to creating dynamically updatable Java applications based on the concept of partitioning applications into units of dynamic updates and illustrate how this approach better addresses the problems of adding update support to existing applications than traditional approaches.