支持Web服務(wù)合成系統(tǒng)可靠性的工作流恢復(fù)機(jī)制的研究
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摘 要
當(dāng)前，Web服務(wù)作為新的分布式計(jì)算技術(shù)，由于其自身的平臺(tái)無(wú)關(guān)、服務(wù)器中立、自描述以及易部署等特性，已經(jīng)被越來(lái)越廣泛地接受。許多企業(yè)已將自身的業(yè)務(wù)能力以Web服務(wù)的形式提供給消費(fèi)者。在眾多的Web服務(wù)出現(xiàn)時(shí)，一個(gè)新的商機(jī)出現(xiàn)了——合成的Web服務(wù)，即將現(xiàn)有的Web服務(wù)重新整合起來(lái)，以形成一個(gè)功能更強(qiáng)大的Web服務(wù)。Web服務(wù)合成是一個(gè)企業(yè)通過(guò)合成基本的Web服務(wù),來(lái)提供給用戶增值服務(wù)的能力。
對(duì)于合成后的平臺(tái)，如何保證系統(tǒng)運(yùn)行的可靠性是一個(gè)必須要解決的問(wèn)題。Internet環(huán)境的開(kāi)放式、分布式的特點(diǎn)使得構(gòu)建于其上的系統(tǒng)更加難以控制；網(wǎng)絡(luò)傳輸?shù)目煽啃员旧砭褪艿狡涞讓佑布脚_(tái)穩(wěn)定性的制約；Web服務(wù)自身異構(gòu)性、自治性和無(wú)狀態(tài)性的特點(diǎn)也大大增加了保證合成平臺(tái)可靠性的難度。而且，Web服務(wù)合成的實(shí)現(xiàn)方法也是影響其可靠性的重要因素。
目前，基于工作流技術(shù)的合成已成為Web服務(wù)合成的重要方法。工作流是描述一個(gè)企業(yè)或組織的業(yè)務(wù)處理過(guò)程的模型，一直是企業(yè)界和學(xué)術(shù)界的熱點(diǎn)研究領(lǐng)域。在本系統(tǒng)設(shè)計(jì)和實(shí)現(xiàn)之前，我們?cè)诠ぷ髁黝I(lǐng)域已經(jīng)取得了一定的研究成果——完全分布式的面向大規(guī)模復(fù)雜應(yīng)用的工作流管理系統(tǒng)ScopeWork。該系統(tǒng)對(duì)包括恢復(fù)處理在內(nèi)的多項(xiàng)工作流技術(shù)均提出了較為完備的解決方案。
現(xiàn)在，Web服務(wù)的合成正是應(yīng)用了工作流的技術(shù)，在完全自治的Web服務(wù)上搭建合成平臺(tái)。因此，基于Web服務(wù)合成系統(tǒng)可靠性的保證完全可以借鑒工作流恢復(fù)的思想。本文提出的系統(tǒng)正是基于ScopeWork系統(tǒng)的研究基礎(chǔ)，利用已掌握的、較為成熟的工作流技術(shù)來(lái)實(shí)現(xiàn)Web服務(wù)的合成。為了保證合成系統(tǒng)的運(yùn)行可靠性，我們?cè)O(shè)計(jì)并實(shí)現(xiàn)了一個(gè)恢復(fù)系統(tǒng)，該系統(tǒng)包括檢測(cè)模塊、監(jiān)控模塊和恢復(fù)模塊，分別完成故障檢測(cè)、流程監(jiān)控及恢復(fù)處理等功能。為了更好地滿足合成系統(tǒng)可靠性的要求，我們從多個(gè)方面對(duì)工作流的恢復(fù)理論進(jìn)行了擴(kuò)展：對(duì)系統(tǒng)中可能出現(xiàn)的運(yùn)行異常重新進(jìn)行分類；對(duì)傳統(tǒng)工作流中的任務(wù)結(jié)構(gòu)模型進(jìn)行了擴(kuò)展；根據(jù)本系統(tǒng)的特點(diǎn)提出了面向系統(tǒng)不同層次的三層異常檢測(cè)模型；針對(duì)合成系統(tǒng)中不同類型的流程，我們分別采用不同的恢復(fù)策略來(lái)處理異常情況。通過(guò)這些工作，我們大大提高了系統(tǒng)的錯(cuò)誤處理能力。

關(guān)鍵詞 Web服務(wù)合成 工作流 恢復(fù) 故障檢測(cè) 錯(cuò)誤處理
Research of Workflow Recovery Mechanism Supporting Reliability of Web Service Composition System
Abstract
Web service, as a new distributed computing technology, has been accepted currently because of its features such as platform independence, server neutrality and self-description. Now many enterprises provide consumers with business ability in manner of Web service. With more and more Web services’ coming forth, a new commerce opportunity, composition of Web services, appears. We can distribute a more powerful Web service, which is composed of existing Web services, to provide added value.
When compositing, we must take into account system reliability. Open and distributed Internet environment makes systems based on it difficult to control; Reliability of network transmission is restricted because of its underlying hardware; The feature of heterogeneity, autonomy and status independence also greatly increases difficulty. Furthermore, the way of composition is also an important factor that will infect system reliability.
Workflow technology has become the most important way of compositing Web services. Workflow, as a hotspot in both academe and business field, is a model that describes handling process inside an enterprise or organization. Before our work on composition system, we have got deeply research in the field of workflow and developed a wholly distributed WFMS ScopeWork, which have put forward a full resolution, including error handling.
Since we use workflow technology to composite Web services, when we try to ensure the reliability of composition system, we can use theory of workflow recovery for reference. The system this thesis advanced is just based on the research of WFMS ScopeWork. To ensure its reliability, we design and implement a recovery system, including detecting module, monitoring module and recovery module, which accomplish the function of failure detecting, process monitoring and recovery handling respectively. To satisfy the reliability requirement, we extend theory of workflow recovery in many aspects, including renewedly classifying runtime exceptions, extending task structure, advancing a three-level failure detecting module oriented different levels of the composition system, using different recovery strategies to handle different types of flows. In summary, we enhance ability of error handling greatly in composition system of Web services.

Key words Web service composition, workflow, recovery, failure detection, error handling目錄
聲 明 I
摘 要 II
ABSTRACT IV
目錄 VI
第一章 引言 1
1.1 問(wèn)題的提出 1
1.2 當(dāng)前的研究現(xiàn)狀 4
1.3 本文的組織結(jié)構(gòu) 5
第二章 關(guān)鍵技術(shù) 7
2.1 Web服務(wù) 7
2.1.1 Web服務(wù)的定義 7
2.1.2 Web服務(wù)的體系結(jié)構(gòu) 8
2.1.3 Web服務(wù)的特點(diǎn) 9
2.1.4 Web服務(wù)的標(biāo)準(zhǔn) 11
2.2 Web服務(wù)合成 13
2.2.1什么是Web服務(wù)合成 13
2.2.2 Web服務(wù)合成的主要問(wèn)題 13
2.2.3 Web服務(wù)合成的方法 15
2.3 工作流技術(shù) 15
2.3.1 工作流的提出 15
2.3.2 工作流管理系統(tǒng) 16
2.3.3 工作流的基本概念 17
2.3.4 工作流管理系統(tǒng)的體系結(jié)構(gòu) 18
2.4 工作流恢復(fù)技術(shù) 20
2.4.1 工作流恢復(fù)的研究現(xiàn)狀 20
2.4.2 先進(jìn)事務(wù)模型（ATM） 21
2.4.3 工作流中的異常及其分類 24
2.4.4 工作流的恢復(fù)策略 24
2.4.5 工作流的恢復(fù)手段 25
第三章 恢復(fù)系統(tǒng)的總體結(jié)構(gòu) 27
3.1 開(kāi)發(fā)環(huán)境 27
3.2 恢復(fù)系統(tǒng)結(jié)構(gòu)框架 29
第四章 日志記錄及流程監(jiān)控 33
4.1 任務(wù)結(jié)構(gòu)的擴(kuò)展 33
4.2 日志倉(cāng)儲(chǔ)結(jié)構(gòu) 35
4.3 日志的記錄 35
4.4 流程監(jiān)控器的設(shè)計(jì) 37
第五章 故障檢測(cè)機(jī)制 39
5.1 “錯(cuò)誤”建模 39
5.2 三層檢測(cè)模型 41
第六章 恢復(fù)策略 44
6.1 Web服務(wù)合成流程的種類 44
6.2兩種恢復(fù)策略 45
總結(jié)與展望 48
參考文獻(xiàn) 49
攻研期間論文發(fā)表情況 51
攻研期間科研情況 52
致 謝 53

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