Preemptive Software Transactional Memory

In state-of-the-art Software Transactional Memory (STM) systems, threads carry out the execution of transactions as non-interruptible tasks. Hence, a thread can react to the injection of a higher priority transactional task and take care of its processing only at the end of the currently executed transaction. In this article we pursue a paradigm shift where the execution of an in-memory transaction is carried out as a preemptable task, so that a thread can start processing a higher priority transactional task before finalizing its current transaction. We achieve this goal in an application-transparent manner, by only relying on Operating System facilities we include in our preemptive STM architecture. With our approach we are able to re-evaluate CPU assignment across transactions along a same thread every few tens of microseconds. This is mandatory for an effective priority-aware architecture given the typically finer-grain nature of in-memory transactions compared to their counterpart in database systems. We integrated our preemptive STM architecture with the TinySTM package, and released it as open source. We also provide the results of an experimental assessment of our proposal based on running a port of the TPC-C benchmark to the STM environment

Towards an aspect weaving BPEL engine

This position paper proposes the use of dynamic aspects and the visitor design pattern to obtain a highly configurable and extensible BPEL engine. Using these two techniques, the core of this infrastructural software can be customised to meet new requirements and add features such as debugging, execution monitoring, or changing to another Web Service selection policy. Additionally, it can easily be extended to cope with customer-specific BPEL extensions. We propose the use of dynamic aspects not only on the engine itself but also on the workflow in order to tackle the problems of Web Service hot deployment and hot fixes to long running processes. In this way, composing aWeb Service "on-the-fly" means weaving its choreography interface into the workflow

Proceedings of the ECSCW'95 Workshop on the Role of Version Control in CSCW Applications

The workshop entitled "The Role of Version Control in Computer Supported Cooperative Work Applications" was held on September 10, 1995 in Stockholm, Sweden in conjunction with the ECSCW'95 conference. Version control, the ability to manage relationships between successive instances of artifacts, organize those instances into meaningful structures, and support navigation and other operations on those structures, is an important problem in CSCW applications. It has long been recognized as a critical issue for inherently cooperative tasks such as software engineering, technical documentation, and authoring. The primary challenge for versioning in these areas is to support opportunistic, open-ended design processes requiring the preservation of historical perspectives in the design process, the reuse of previous designs, and the exploitation of alternative designs. The primary goal of this workshop was to bring together a diverse group of individuals interested in examining the role of versioning in Computer Supported Cooperative Work. Participation was encouraged from members of the research community currently investigating the versioning process in CSCW as well as application designers and developers who are familiar with the real-world requirements for versioning in CSCW. Both groups were represented at the workshop resulting in an exchange of ideas and information that helped to familiarize developers with the most recent research results in the area, and to provide researchers with an updated view of the needs and challenges faced by application developers. In preparing for this workshop, the organizers were able to build upon the results of their previous one entitled "The Workshop on Versioning in Hypertext" held in conjunction with the ECHT'94 conference. The following section of this report contains a summary in which the workshop organizers report the major results of the workshop. The summary is followed by a section that contains the position papers that were accepted to the workshop. The position papers provide more detailed information describing recent research efforts of the workshop participants as well as current challenges that are being encountered in the development of CSCW applications. A list of workshop participants is provided at the end of the report. The organizers would like to thank all of the participants for their contributions which were, of course, vital to the success of the workshop. We would also like to thank the ECSCW'95 conference organizers for providing a forum in which this workshop was possible

State of Watershed Payments: An Emerging Marketplace

A global research effort conducted by Ecosystem Marketplace identified a total of approximately 288 payments for watershed services (PWS) and water quality trading (WQT) programs in varying stages of activity over the past 30 years. In 2008, the baseline year, about 127 programs were actively receiving payments or transacting credits. The total transaction value from all programs actively engaged in 2008 is estimated at US$9.3 billion. Over the entire time span of recorded activity, total transaction value is estimated at slightly more than US$50 billion, impacting some 3.24 billion hectares

Programmability and Performance of Parallel ECS-based Simulation of Multi-Agent Exploration Models

While the traditional objective of parallel/distributed simulation techniques has been mainly in improving performance and making very large models tractable, more recent research trends targeted complementary aspects, such as the “ease of programming”. Along this line, a recent proposal called Event and Cross State (ECS) synchronization, stands as a solution allowing to break the traditional programming rules proper of Parallel Discrete Event Simulation (PDES) systems, where the application code processing a specific event is only allowed to access the state (namely the memory image) of the target simulation object. In fact with ECS, the programmer is allowed to write ANSI-C event-handlers capable of accessing (in either read or write mode) the state of whichever simulation object included in the simulation model. Correct concurrent execution of events, e.g., on top of multi-core machines, is guaranteed by ECS with no intervention by the programmer, who is in practice exposed to a sequential-style programming model where events are processed one at a time, and have the ability to access the current memory image of the whole simulation model, namely the collection of the states of any involved object. This can strongly simplify the development of specific models, e.g., by avoiding the need for passing state information across concurrent objects in the form of events. In this article we investigate on both programmability and performance aspects related to developing/supporting a multi-agent exploration model on top of the ROOT-Sim PDES platform, which supports ECS

The Political Ecology of Takeovers: Thoughts On Harmonizing the European Corporate Governance Environment

Economic policy debate in the United States during the 1980s focused on the dynamics of bidder and target tactics in hostile takeovers. Confronted with the largest transactions in business history, financial economists took advantage of developments in econometric techniques to conduct virtually real time studies of the impact on firm value of each new bidder tactic and target defense. For courts and lawyers, hostile takeovers subjected standard features of corporate law to the equivalent of a stress x-ray, revealing previously undetected doctrinal cracks. Congress held seemingly endless hearings on the subject, although managing to enact only relatively innocuous tax penalties on particular defensive tactics the public found especially offensive. State legislatures, closer to the political action, acted more substantively, if less wisely. Whether or not takeovers created new wealth they did result in its transfer, and at least one of the parties from whom wealth was transferred – target management – had remarkable influence in state legislatures. When labor also came actively to oppose hostile takeovers, the coalition was virtually unstoppable. The decade saw some thirty-four states pass more than sixty-five major laws restricting corporate takeovers, including states discouraging partial offers and front-end loaded offers. The 1980s have now closed transactionally as well as chronologically. The first quarter of 1991 marked the lowest level of merger and acquisition activity since the first quarter of 1980. The passing of this remarkable decade invites a broader perspective, which can be helpfully thought of as the political ecology of takeovers. An ecological perspective builds on the proposition that phenomena are embedded in interactive systems – a rich web of mutually dependent relationships. Thus, a seemingly independent event cannot be fully evaluated without understanding how it relates to the environmental forces to which it was a response and which, in turn, respond to it. What the narrow focus of the 1980s debate missed was an appreciation of the complex economic corporate governance and political environments in which hostile takeovers are embedded. Corporate acquisitions are a response to real conditions in the economic environment. The choice among acquisition techniques, most importantly between friendly and hostile transactions, depends both upon the economic motivation for the transaction and upon conditions in the corporate governance environment. Finally, conditions in the corporate governance environment are directly influenced by politics; both what is allowed and prohibited is defined, in the first instance, by legislation. My goal in this article is two-fold. I begin by sketching the political ecology of takeovers in the United States – the interaction of economics, corporate governance and politics that shaped the experience of the 1980s. I then make a tentative effort at applying the insights gained from an ecological perspective to the current endeavor to change dramatically the European corporate governance environment through the harmonization of takeover and company law in the European Community. Sheltered by the cloak of political naivete commonly allowed those attempting comparative analysis from a distance, I will argue that an ecological understanding of takeovers suggests a different approach than that reflected so far in the debate over the terms of harmonization. This approach is based on what I term the mutability principle

Internet of robotic things : converging sensing/actuating, hypoconnectivity, artificial intelligence and IoT Platforms

The Internet of Things (IoT) concept is evolving rapidly and influencing newdevelopments in various application domains, such as the Internet of MobileThings (IoMT), Autonomous Internet of Things (A-IoT), Autonomous Systemof Things (ASoT), Internet of Autonomous Things (IoAT), Internetof Things Clouds (IoT-C) and the Internet of Robotic Things (IoRT) etc.that are progressing/advancing by using IoT technology. The IoT influencerepresents new development and deployment challenges in different areassuch as seamless platform integration, context based cognitive network integration,new mobile sensor/actuator network paradigms, things identification(addressing, naming in IoT) and dynamic things discoverability and manyothers. The IoRT represents new convergence challenges and their need to be addressed, in one side the programmability and the communication ofmultiple heterogeneous mobile/autonomous/robotic things for cooperating,their coordination, configuration, exchange of information, security, safetyand protection. Developments in IoT heterogeneous parallel processing/communication and dynamic systems based on parallelism and concurrencyrequire new ideas for integrating the intelligent “devices”, collaborativerobots (COBOTS), into IoT applications. Dynamic maintainability, selfhealing,self-repair of resources, changing resource state, (re-) configurationand context based IoT systems for service implementation and integrationwith IoT network service composition are of paramount importance whennew “cognitive devices” are becoming active participants in IoT applications.This chapter aims to be an overview of the IoRT concept, technologies,architectures and applications and to provide a comprehensive coverage offuture challenges, developments and applications