Well adapted to the loosely coupled nature of distributed interaction in large-scale applications, the publish/subscribe communication paradigm has recently received increasing attention. With systems based on the publish/subscribe interaction scheme, subscribers register their interest in an event, or a pattern of events, and are subsequently asynchronously notified of events generated by publishers. Many variants of the paradigm have recently been proposed, each variant being specifically adapted to some given application or network model. This paper factors out the common denominator underlying these variants: full decoupling of the communicating entities in time, space, and synchronization. We use these three decoupling dimensions to better identify commonalities and divergences with traditional interaction paradigms. The many variations on the theme of publish/subscribe are classified and synthesized. In particular, their respective benefits and shortcomings are discussed both in terms of interfaces and implementations.

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The many faces of publish/subscribe

From the Publisher:
Designing application and middleware software to run in concurrent and networked environments is a significant challenge to software developers The patterns catalogued in this second volume of Pattern-Oriented Software Architectures (POSA) form the basis of a pattern language that addresses issues associated with concurrency and networking
The book presents 17 interrelated patterns ranging from idioms through architectural designs They cover core elements of building concurrent and network systems: service access and configuration, event handling, synchronization,
and concurrency All patterns present extensive examples and known uses in multiple programming languages, including C++, C, and Java
The book can be used to tackle specific software development problems or read from cover to cover to provide a fundamental understanding of the best practices for constructing concurrent and networked applications and middleware
About the Authors
This book has been written by the award winning team responsible for the first POSA volume "A System of Patterns", joined in this volume by Douglas C Schmidt from University of California, Irvine (UCI), USA
Visit our Web Page

/pdf/pattern-oriented-software-architecture-patterns-for-53algdjkkg.pdf

Pattern-Oriented Software Architecture, Patterns for Concurrent and Networked Objects

Awareness and use of agile methods has grown rapidly among the information systems development (ISD) community in recent years. Like most previous methods, the development and promotion of these methods have been almost entirely driven by practitioners and consultants, with little participation from the research community during the early stages of evolution. While these methods are now the focus of more and more research efforts, most studies are still based on XP, Scrum, and other industry-driven foundations, with little or no conceptual studies of ISD agility in existence. As a result, this study proposes that there are a number of significant conceptual shortcomings with agile methods and the associated literature in its current state, including a lack of clarity, theoretical glue, parsimony, limited applicability, and naivety regarding the evolution of the concept of agility in fields outside systems development. Furthermore, this has significant implications for practitioners, rendering agile method comparison and many other activities very difficult, especially in instances such as distributed development and large teams that are not conducive to many of the commercial agile methods. This study develops a definition and formative taxonomy of agility in an ISD context, based on a structured literature review of agility across a number of disciplines, including manufacturing and management where the concept originated, matured, and has been applied and tested thoroughly over time. The application of the texonomy in practice is then demonstrated through a series of thought trials conducted in a large multinational organization. The intention is that the definition and taxonomy can then be used as a starting point to study ISD method agility regardless of whether the method is XP or Scrum, agile or traditional, complete or fragmented, out-of-the-box or in-house, used as is or tailored to suit the project context.

https://ulir.ul.ie/bitstream/handle/10344/574/L%201.pdf;sequence=2

Agility from First Principles: Reconstructing the Concept of Agility in Information Systems Development

Cyber-physical systems (CPSs) are the next generation of engineered systems in which computing, communication, and control technologies are tightly integrated. Research on CPSs is fundamentally important for engineered systems in many important application domains such as transportation, energy, and medical systems. We overview CPS research from both a historical point of view in terms of technologies developed for early generations of control systems, as well as recent results on CPSs in many relevant research domains such as networked control, hybrid systems, real-time computing, real-time networking, wireless sensor networks, security, and model-driven development. We outline the potential for CPSs in many societally important application domains.

http://cesg.tamu.edu/wp-content/uploads/2012/03/ps_files/12-02-10-CPS-Centennial.pdf

Cyber–Physical Systems: A Perspective at the Centennial

Components have long promised to encapsulate data and programs into a box that operates predictably without requiring that users know the specifics of how it does so. Many advocates have predicted that components will bring about widespread software reuse, spawning a market for components usable with such mainstream software buses as the Common Object Request Broker Architecture (CORBA) and the Distributed Component Object Model (DCOM). In the Windows world, at least, this prediction is becoming a reality. Yet recent reports indicate mixed results when using and reusing components in mission-critical settings. Such results raise disturbing questions. How can you trust a component? What if the component behaves unexpectedly, either because it is faulty or simply because you misused it? Before we can trust a component in mission-critical applications, we must be able to determine, reliably and in advance, how it will behave. In this article the authors define a general model of sofware contracts and show how existing mechanisms could be used to turn traditional components into contract-aware ones.

/pdf/making-components-contract-aware-2wyid6dodq.pdf

Making components contract aware

https://www.dre.vanderbilt.edu/~schmidt/PDF/TAO.pdf

The design of the TAO real-time object request broker

The CORBA Event Service provides a flexible model for asynchronous communication among objects. However, the standard CORBA Event Service specification lacks important features required by real-time applications. For instance, operational flight programs for fighter aircraft have complex real-time processing requirements. This paper describes the design and performance of an object-oriented, real-time implementation of the GORBA Event Service that is designed to meet these requirements.This paper makes three contributions to the design and performance measurement of object-oriented real-time systems. First, it illustrates how to extend the CORBA Event Service so that it is suitable for real-time systems. These extensions support periodic rate-based event processing and efficient event filtering and correlation. Second, it describes how to develop object-oriented event dispatching and scheduling mechanisms that can provide real-time guarantees. Finally, the paper presents benchmarks that demonstrate the performance tradeoffs of alternative concurrent dispatching mechanisms for real-time Event Services.

/pdf/the-design-and-performance-of-a-real-time-corba-event-3mtp4pvyua.pdf

The design and performance of a real-time CORBA event service

There is increasing demand to extend CORBA middleware to support applications with stringent quality of service (QoS) requirements. However, conventional CORBA middleware does not define standard features to dynamically schedule operations for applications that possess deterministic real-time requirements. This paper presents three contributions to the study of real-time CORBA operation scheduling strategies. First, we document our evolution from static to dynamic scheduling for applications with deterministic real-time requirements. Second, we describe the flexible scheduling service framework in our real-time CORBA implementation, TAO, which supports core scheduling strategies efficiently. Third, we present results from empirical benchmarks that quantify the behavior of these scheduling strategies and assess the overhead of dynamic scheduling in TAO. Our empirical results using TAO show that dynamic scheduling of CORBA operations can be deterministic and can achieve acceptable latency for operations, even with moderate levels of queueing.

/pdf/the-design-and-performance-of-a-real-time-corba-7zf7c2mae6.pdf

The Design and Performance of a Real-Time CORBA SchedulingService

The paper describes the design and performance of a real time I/O (RIO) subsystem that supports real time applications running on off-the-shelf hardware and software. The paper provides two contributions to the study of real time I/O subsystems. First it describes how RIO supports end-to-end, prioritized traffic to bound the I/O utilization of each priority class and eliminates the key sources of priority inversion in I/O subsystems. Second, it illustrates how a real time I/O subsystem can reduce latency bounds on end-to-end communication between high-priority clients without unduly penalizing low priority and best-effort clients.

https://www.dre.vanderbilt.edu/~schmidt/PDF/RIO.pdf

The design and performance of a real-time I/O subsystem

Next-generation distributed interactive simulations (DISs) will have stringent quality of service (QoS) requirements for throughput, latency and scalability, as well as requirements for a flexible communication infrastructure to reduce software lifecycle costs. The CORBA event service provides a flexible model for asynchronous communication among distributed and collocated objects. However, the standard CORBA event service specification lacks important features and QoS optimizations required by DIS systems. This paper makes five contributions to the design, implementation and performance measurement of DIS systems. First, it describes how the CORBA event service can be implemented to support key QoS features. Second, it illustrates how to extend the CORBA event service so that it is better suited for DISs. Third, it describes how to develop efficient event dispatching and scheduling mechanisms that can sustain high throughput. Fourth, it describes how to use multicast protocols to reduce network traffic transparently and to improve system scalability. Finally, it illustrates how an event service framework can be strategized to support configurations that facilitate high throughput, predictable bounded latency, or some combination of each.

/pdf/applying-a-scalable-corba-event-service-to-large-scale-hueba9tpt3.pdf

David L. Levine

Papers

The design of the TAO real-time object request broker

The design and performance of a real-time CORBA event service

The Design and Performance of a Real-Time CORBA SchedulingService

The design and performance of a real-time I/O subsystem

Applying a scalable CORBA event service to large-scale distributed interactive simulations