Transaction processing in a peer to peer database network

This paper investigates a transaction processing mechanism in a peer to peer database network. A peer to peer database network is a collection of autonomous data sources, called peers, where each peer augments a conventional database management system with an inter-operability layer (i.e. mappings) for sharing data. In this network, each peer independently manages its database and executes queries as well as updates over the related data in other peers. In this paper, we consider a peer to peer database network where mappings between peers are established through data-level mappings for sharing data and resolving data heterogeneity. With regards to transaction processing in a peer to peer database network, we mainly focus on how to maintain a consistent execution view of concurrent transactions in peers without a global transaction coordinator. Since there is no global transaction coordinator and each peer executes concurrent transactions independently, different peers may produce different execution views for the same set of transactions. For this purpose, we investigate potential problems that arise when maintaining a consistent execution of concurrent transactions. In order to guarantee consistent execution, we introduce a correctness criteria and propose two approaches, namely Merged Transactions and OTM based propagation. We assume that one single peer initiates the concurrent transactions. We also present a solution for ensuring the consistent execution view of concurrent transactions considering the failures of transactions.     

一种Web服务组合事务框架的设计与实现

Web服务组合已成为跨企业应用集成的主要方法,服务组合需要事务机制来保证其可靠性。由于服务组合自身的特点,传统事务处理方法不适合。首先总结服务组合事务的特点,提出了基于层次的服务组合事务框架,并详细分析了服务组合事务的协调过程。最后给出了服务组合事务协调协议并实现了服务组合事务服务原型系统。     

一个基于共享内存的企业级Web服务事务处理模型研究

Web服务事务处理必须提供协调短事务和长事务的能力。本文提出了一个基于共享内存的Web服务事务处理模型,在以．Net为开发工具实现企业级信息管理系统时,利用现有技术,不对Web Service进行任何扩展,在Web Serice中处理原子事务和内聚事务。     

Web服务事务处理的模型化方法研究

Web服务技术的出现为解决跨组织的过程集成问题提供了一种模式。在集成和交互的过程中,Web服务需要事务的支持来保持数据的一致性。传统协议规范已经能够支持Web服务下的事务处理,但仍然存在着问题,比如不同事务处理规范之间兼容性处理、消息格式不匹配、补偿机制、超时和事务范围确立等问题还有待解决。本文介绍了一种Web服务系统的层次设计,并给出了一种Web服务事务处理的模型化方法。这种方法在设计初期就对事务的补偿机制、超时和事务范围这些问题进行考虑和解决,使事务处理过程更加清晰和直接。     

异步Web Services的可靠性探讨

Web服务是面向服务的开发模式和Web技术共同发展的结果,采用现有的网络协议如HTTP,FTP或者SMTP作为传输载体,使用基于XML的XML-RPC或者SOAP作为远程调用和消息传输的数据标准.由于其松散的噪成结构,可靠性成了Web服务推广的最大瓶颈.本文通过对异步Web Services的消息类型和事务管理进行了一定的探讨,给出了消息的分类标准和初步的事务模型.     

A survey on the history of transaction management: from flat to grid transactions

Transactions have been around since the Seventies to provide reliable information processing in automated information systems. Originally developed for simple ‘debit-credit’ style database operations in centralized systems, they have moved into much more complex application domains including aspects like distribution, process-orientation and loose coupling. The amount of published research work on transactions is huge and a number of overview papers and books already exist. A concise historic analysis providing an overview of the various phases of development of transaction models and mechanisms in the context of growing complexity of application domains is still missing, however. To fill this gap, this paper presents a historic overview of transaction models organized in several ‘transaction management eras’, thereby investigating numerous transaction models ranging from the classical flat transactions, via advanced and workflow transactions to the Web Services and Grid transaction models. The key concepts and techniques with respect to transaction management are investigated. Placing well-known research efforts in historical perspective reveals specific trends and developments in the area of transaction management. As such, this paper provides a comprehensive, structured overview of developments in the area.     

基于细胞膜模型的Web Service事务管理

随着大量传统应用程序向Web Service的转变,多个Web Service的组合应用成为Web Service发展的趋势.提出了Web Service事务的一套管理模型,该模型是受到生物学里细胞膜模型的启发,根据细胞膜模型与Web Service事务管理的相似性而得出的.在此基础上,给出了一个简单的应用实例.最后对其发展的方向提出了自己的一些看法.     

A Formal Framework for Web Services Coordination

Recently the term Web Services Choreography has been introduced to address some issues related to Web Services Composition and Coordination. Several proposals for describing Choreography for Business Processes have been presented in the last years and many of these languages (e.g. BPEL4WS) make use of concepts as long-running transactions and compensations for coping with error handling. However, the complexity of BPEL4WS makes it difficult to formally define this framework, thus limiting the formal reasoning about the designed applications. In this paper, we formally address Web Services Coordination with particular attention to Web transactions. We enhance our past work - the Event Calculus - introducing two main novelties: i) a multicast event notification mechanism, and ii) event scope names binding. The former enables an easier specification of complex coordination scenarios — such as E-commerce applications require — while the latter allows many new interesting behaviors which can be very useful in business scenarios: the introduction of private event scope names — used to deal with security and privacy — and a dynamic event scopes definition that can be used to manage multiple instances of the same application.     

基于Web服务的工作流事务处理的研究与实现

事务处理是Web服务实现分布式信息集成的关键技术之一,利用工作流技术实现Web服务的事务处理是实现分布式事务的一种有效手段.提出一个能够处理分布式、异构应用下Web服务组合事务的模型,并详述Web服务事务在执行过程中抛出异常时,补偿事务的产生策略和执行机制.     

基于预申请和功能替代的Web服务流程事务模型

Web服务的出现是Internet技术发展的一次革命,使得Web上的交互方式从以信息为中心转化为以服务为中心,从而使Internet上的各种应用集成成为可能。目前,各个标准化组织制定了许多Web的服务流程协作规范,在业务流程管理（BPM）上得到了广泛的直用,如：电子商务、企业间的应用集成等。事务为流程协作提供了可靠性保障,当前的Web服务流程协作规范对事务的支持主要基于补偿事务,然而通过补偿回滚已完成的事务代价较大。为了尽可能地减少补偿回滚的发生,提高Web服务流程事务的成功率,提出了基于预申请和功能替代的Web服务流程事务模型。该模型提出的预申请阶段完成了对关键资源的预定,减少了并发冲突;另一方面,该模型提出的功能替代整合了Internet／Intranet上存在的许多功能语义相同的Web服务,从而大大地提高Web服务流程事夸的成功率。     

Chronological scheduling of transactions with temporal dependencies

Database applications often impose temporal dependencies between transactions that must be satisfied to preserve data consistency. The extant correctness criteria used to schedule the execution of concurrent transactions are either time independent or use strict, difficult to satisfy real-time constraints. On one end of the spectrum, serializability completely ignores time. On the other end, deadline scheduling approaches consider the outcome of each transaction execution correct only if the transaction meets its real-time deadline. In this article, we explore new correctness criteria and scheduling methods that capture temporal transaction dependencies and belong to, the broad area between these two extreme approaches. We introduce the concepts ofsuccession dependency andchronological dependency and define correctness criteria under which temporal dependencies between transactions are preserved even if the dependent transactions execute concurrently. We also propose achronological scheduler that can guarantee that transaction executions satisfy their chronological constraints. The advantages of chronological scheduling over traditional scheduling methods, as well as the main issues in the implementation and performance of the proposed scheduler, are discussed.     

taTHP：一种THP的改进事务模型

随着电子商务的迅速崛起,Web服务逐渐成为Web领域一个崭新的分布式计算模型.在自治的、松耦合的Web服务事务环境中,由于事务参与者不能提供长时排它的资源锁定模式,因而无法继续采用传统的ACID事务结构.换而言之,Web服务事务处理必须具备针对松散耦合事务环境及自治资源提供策略的协调能力.本文在THP(TentativeHoldProtocol)事务模型的基础上,进一步发展了资源的“准”占用思想,提出了一种具备“事务意识”的新型资源协调算法,从而使系统性能有了较大提升.     

Concurrency control for step-decomposed transactions

The throughput of a transaction processing system can be improved by decomposing transactions into steps and allowing the steps of concurrent transactions to be interleaved. In some cases all interleavings are assumed to be acceptable; in others certain interleavings are forbidden. In this paper we describe a new concurrency control that guarantees that only acceptable interleavings occur. We describe the implementation of the new control within the CA-Open Ingres^tm database management system and experiments that were run to evaluate its effectiveness using the TPC-C^tm Benchmark Transactions. The experiments demonstrate up to 80% improvement when lock contention is high, when long running transactions are a part of the transaction suite, and/or when sufficient system resources are present to support the additional concurrency that the new control allows. Finally, we describe a new correctness criterion that is weaker than serializability and yet guarantees that the specifications of all transactions are met. The criterion can be used to determine the acceptable interleavings for a particular application. The specification of these interleavings can serve as input to the new control.     

taTHP: 一种THP的改进事务模型

随着电子商务的迅速崛起,Web服务逐渐成为Web领域一个崭新的分布式计算模型.在自治的、松耦合的Web服务事务环境中,由于事务参与者不能提供长时排它的资源锁定模式,因而无法继续采用传统的ACID事务结构.换而言之,Web服务事务处理必须具备针对松散耦合事务环境及自治资源提供策略的协调能力.本文在THP(TentativeHoldProtocol)事务模型的基础上,进一步发展了资源的“准”占用思想,提出了一种具备“事务意识”的新型资源协调算法,从而使系统性能有了较大提升.     

An analysis of web services support for dynamic business process outsourcing

Outsourcing of business processes is crucial for organizations to be effective, efficient and flexible. In fast changing markets, dynamic outsourcing is required, in which business relationships are established and enacted on-the-fly in an adaptive, fine-grained way. This requires automated means for the establishment of outsourcing relationships and for the enactment of services performed in these relationships. Due to wide industry support and their model of loose coupling, Web Services have become the mechanism of choice to interconnect organizations. This paper analyzes Web Services support for the dynamic process outsourcing paradigm. We discuss contract-based outsourcing to define requirements, introduce the Web Services framework and investigate the match between the two. We observe that the framework requires further support for cross-organizational business processes and mechanisms for contracting, QoS management and transaction management. We suggest an approach to fill these gaps based on a business process support application layer implemented on Web Service technology.     

Supporting dynamic access to virtualized data resources via WSRF-based services

Today grid applications require not only lots of computational power but data at a very large scale too. Although grid computing was initially conceptualized as the technology that focuses on solving compute-intensive problems, this focus has gradually shifted to applications where data is distributed over various locations. Access to these data resources stored in heterogeneous grid storage systems located at geographically distributed virtual organizations in an integrated and uniform way is a challenging problem. The Web Services Resource Framework (WSRF) has recently emerged as the standard for the development and integration of grid services. This paper proposes and presents Gravy4WS, a middleware architecture based on WSRF Web services that enables the dynamic access to virtualized grid data resources. A novel scheduling algorithm called DCE (Delegating-Cluster-Execution based Scheduling) is proposed to improve load balancing of the system. The implementation of Gravy4WS using WSRF libraries and services provided by Globus Toolkit 4 is described together with its performance evaluation.     

Web服务事务中的补偿机制研究与实现

可靠的web服务事务机制是面向服务的架构（SOA）中不可缺少的要素之一,它本身也需要有一定的恢复机制,其中非常重要的技术就是事务补偿。结合Web服务事务的特点,以及数据库系统中的触发器技术,可以为Web服务的事务处理模型提供一个半自动的事务补偿机制。     

FENECIA: failure endurable nested-transaction based execution of composite Web services with incorporated state analysis

Interest in the Web services (WS) composition (WSC) paradigm is increasing tremendously. A real shift in distributed computing history is expected to occur when the dream of implementing Service-Oriented Architecture (SOA) is realized. However, there is a long way to go to achieve such an ambitious goal. In this paper, we support the idea that, when challenging the WSC issue, the earlier that the inevitability of failures is recognized and proper failure-handling mechanisms are defined, from the very early stage of the composite WS (CWS) specification, the greater are the chances of achieving a significant gain in dependability. To formalize this vision, we present the FENECIA (Failure Endurable Nested-transaction based Execution of Composite Web services with Incorporated state Analysis) framework. Our framework approaches the WSC issue from different points of view to guarantee a high level of dependability. In particular, it aims at being simultaneously a failure-handling-devoted CWS specification, execution, and quality of service (QoS) assessment approach. In the first section of our framework, we focus on answering the need for a specification model tailored for the WS architecture. To this end, we introduce WS-SAGAS, a new transaction model. WS-SAGAS introduces key concepts that are not part of the WS architecture pillars, namely, arbitrary nesting, state, vitality degree, and compensation, to specify failure-endurable CWS as a hierarchy of recursively nested transactions. In addition, to define the CWS execution semantics, without suffering from the hindrance of an XML-based notation, we describe a textual notation that describes a WSC in terms of definition rules, composability rules, and ordering rules, and we introduce graphical and formal notations. These rules provide the solid foundation needed to formulate the execution semantics of a CWS in terms of execution correctness verification dependencies. To ensure dependable execution of the CWS, we present in the second section of FENECIA our architecture THROWS, in which the execution control of the resulting CWS is distributed among engines, discovered dynamically, that communicate in a peer-to-peer fashion. A dependable execution is guaranteed in THROWS by keeping track of the execution progress of a CWS and by enforcing forward and backward recovery. We concentrate in the third section of our approach on showing how the failure consideration is trivial in acquiring more accurate CWS QoS estimations. We propose a model that assesses several QoS properties of CWS, which are specified as WS-SAGAS transactions and executed in THROWS. We validate our proposal and show its feasibility and broad applicability by describing an implemented prototype and a case study.     

嵌入式实时数据库ARTs-EDB事务调度实现技术

着重讨论了嵌入式实时数据库系统ARTs-EDB中事务调度实现技术。给出了ARTs-EDB中事务的执行模型、状态及状态变迁；设计了一个考虑事务类型和截止期的多层动态可调整优先级分派方法；给出了一个优先级驱动可抢占的实时事务调度策略，以保证更多事务满足截止期要求。     

Semantic Based Concurrency Control of Open Nested Transactions in Active Object Oriented Database Management Systems

Active object oriented database management systems (AODBMS) are finding increasing application in different application domains and especially for cooperative and long duration activity management. In this paper, we propose a concurrency control mechanism for open nested transactions in an AODBMS. It exploits the semantics of the transactions to achieve controlled cooperation and concurrency among the transactions. Atomic AODBMS transactions are treated as base transactions. A complex transaction type is formed from a collection of base and complex transactions, a set of detached mode ECA rules and a state transition model. The cooperation semantics of a complex transaction type with other complex transaction types is specified by associating with each state of a complex transaction, a set of cooperating complex transaction types. The abort semantics of a complex transaction type is specified by means of compensating base transactions. We define a correct class of schedule called CoopComp-schedule which satisfies the state transition semantics of the individual complex transactions and also maintains the cooperation and compensation semantics of the individual complex transactions within the generated schedule. A concurrency control scheme called NP-QuadLock for generating only CoopComp-schedules has been provided. The proof of correctness of the proposed concurrency control mechanism is also given.