RAFDA: A Policy-Aware Middleware Supporting the Flexible Separation of Application Logic from Distribution

Middleware technologies often limit the way in which object classes may be used in distributed applications due to the fixed distribution policies that they impose. These policies permeate applications developed using existing middleware systems and force an unnatural encoding of application level semantics. For example, the application programmer has no direct control over inter-address-space parameter passing semantics. Semantics are fixed by the distribution topology of the application, which is dictated early in the design cycle. This creates applications that are brittle with respect to changes in distribution. This paper explores technology that provides control over the extent to which inter-address-space communication is exposed to programmers, in order to aid the creation, maintenance and evolution of distributed applications. The described system permits arbitrary objects in an application to be dynamically exposed for remote access, allowing applications to be written without concern for distribution. Programmers can conceal or expose the distributed nature of applications as required, permitting object placement and distribution boundaries to be decided late in the design cycle and even dynamically. Inter-address-space parameter passing semantics may also be decided independently of object implementation and at varying times in the design cycle, again possibly as late as run-time. Furthermore, transmission policy may be defined on a per-class, per-method or per-parameter basis, maximizing plasticity. This flexibility is of utility in the development of new distributed applications, and the creation of management and monitoring infrastructures for existing applications.Comment: Submitted to EuroSys 200

Proactive multi-tenant cache management for virtualized ISP networks

The content delivery market has mainly been dominated by large Content Delivery Networks (CDNs) such as Akamai and Limelight. However, CDN traffic exerts a lot of pressure on Internet Service Provider (ISP) networks. Recently, ISPs have begun deploying so-called Telco CDNs, which have many advantages, such as reduced ISP network bandwidth utilization and improved Quality of Service (QoS) by bringing content closer to the end-user. Virtualization of storage and networking resources can enable the ISP to simultaneously lease its Telco CDN infrastructure to multiple third parties, opening up new business models and revenue streams. In this paper, we propose a proactive cache management system for ISP-operated multi-tenant Telco CDNs. The associated algorithm optimizes content placement and server selection across tenants and users, based on predicted content popularity and the geographical distribution of requests. Based on a Video-on-Demand (VoD) request trace of a leading European telecom operator, the presented algorithm is shown to reduce bandwidth usage by 17% compared to the traditional Least Recently Used (LRU) caching strategy, both inside the network and on the ingress links, while at the same time offering enhanced load balancing capabilities. Increasing the prediction accuracy is shown to have the potential to further improve bandwidth efficiency by up to 79%

Flexible Management on BSP Process Rescheduling: Offering Migration at Middleware and Application Levels

This article describes the rationales for developing jMigBSP - a Java programming library that offers object rescheduling. It was designed to work on grid computing environments and offers an interface that follows the BSP (Bulk Synchronous Parallel) style. jMigBSP’s main contribution focuses on the rescheduling facility in two different ways: (i) by using migration directives on the application coded irectly and (ii) through automatic load balancing at middleware level. Especially, this second idea is feasible thanks to the Java’s inheritance feature, in which transforms a simple jMigBSP application in amigratable one only by changing a single line of code. In addition, the presented library makes the object interaction easier by providing one-sided message passing directives and hides network latency through asynchronous communications. Finally, we developed three BSP applications: (i) Prefix Sum; (ii) Fractal Image Compression (FIC) and; (iii) Fast Fourier Transform (FFT).They show our library as viable solution to offer load balancing on BSP applications. Specially, the FIC results present gains up to 37% when applying migration directives inside the code. Finally, the FFT tests emphasize strength of jMigBSP. In this situation, it outperforms a native library denoted BSPlib when migration facilities take place.Keywords: Bulk Synchronous Parallel, rescheduling, Java, adaptation, object migration, grid computing

Museums as disseminators of niche knowledge: Universality in accessibility for all

Accessibility has faced several challenges within audiovisual translation Studies and gained great opportunities for its establishment as a methodologically and theoretically well-founded discipline. Initially conceived as a set of services and practices that provides access to audiovisual media content for persons with sensory impairment, today accessibility can be viewed as a concept involving more and more universality thanks to its contribution to the dissemination of audiovisual products on the topic of marginalisation. Against this theoretical backdrop, accessibility is scrutinised from the perspective of aesthetics of migration and minorities within the field of the visual arts in museum settings. These aesthetic narrative forms act as modalities that encourage the diffusion of ‘niche’ knowledge, where processes of translation and interpretation provide access to all knowledge as counter discourse. Within this framework, the ways in which language is used can be considered the beginning of a type of local grammar in English as lingua franca for interlingual translation and subtitling, both of which ensure access to knowledge for all citizens as a human rights principle and regardless of cultural and social differences. Accessibility is thus gaining momentum as an agent for the democratisation and transparency of information against media discourse distortions and oversimplifications

Componentising a scientific application for the grid

CoreGRID is a Network of Excellence funded by the European Commission under the Sixth Framework Programm