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Systems that provide distributed multimedia services are subject to constant evolution; customizable middleware is required to effectively manage this change. Middleware services for resource management execute concurrently with each other, and with application activities, and can, therefore, potentially interfere with each other. To ensure cost-effective QoS in distributed multimedia systems, safe composability of resource management services is essential. In this article, we present a meta-architectural framework, the Two-Level Actor Model (TLAM) for customizable QoS-based middleware, based on the actor model of concurrent active objects. Using TLAM, a semantic model for specifying and reasoning about components of open distributed systems, we show how a QoS brokerage service can be used to coordinate multimedia resource management services in a safe, flexible, and efficient manner. In particular, we show a system in which the multimedia actor behaviors satisfy the specified requirements and provide the required multimedia service. The behavior specification leaves open the possibility of a variety of algorithms for resource management. Furthermore, constraints are identified that are sufficient to guarantee noninterference among the multiple broker resource management services, as well as providing guidelines for the safe composition of additional services. [ABSTRACT FROM AUTHOR]

The AGERE! workshop 1 has been organized with the ACM SPLASH conference since 2011. The workshop has brought together researchers in programming systems, languages, and applications based on actors, active/concurrent objects, agents, and more broadly, high-level programming paradigms which facilitate decentralized control. The goal of the workshop is to promote use of such paradigms to address the problem of developing software for complex, real-world applications. The AGERE workshop is a follow on to workshops on Object-based Concurrent Programming which were organized twenty years earlier in conjunction with OOPSLA [1–3] . In the last two decades, concurrency and distribution have become part of everyday programming. In this context, the objective of AGERE! is to foster the development and adoption of high-level programming paradigms embracing concurrency at the core of the developed abstractions and constructs. This special issue collects extended and enhanced versions of selected papers from AGERE! 2011 and 2012 which underwent additional review cycles. [ABSTRACT FROM AUTHOR]

Session types have been proposed as a means of statically verifying implementations of communication protocols. Although prior work has been successful for some classes of protocols, it does not cope well with parameterized, multi-actor scenarios with inherent asynchrony. For example, the sliding window protocol is not expressible in previously proposed session type notations. This article defines System-A: a novel session type system, as well the associated programming language that together overcome many of the limitations of prior work. With explicit support for asynchrony and concurrency, as well as multiple forms of parameterization, we demonstrate that System-A can be used for the static verification of a large class of asynchronous communication protocols. [ABSTRACT FROM AUTHOR]