隨著科技的發展，人們越來越依賴日常生活中各種軟體應用程式所提供的服務。其日益增長的規模及複雜度使得人們對於軟體品質有更高的要求。在過去研究發表中，許多軟體可靠度成長模型成功地用於評估軟體品質，部分研究亦證明將無限和有限服務器排隊系統用於錯誤移除過程建模中是有效的。然而，這些無限和有限服務器模型大多假設除錯的過程是遵照先到先服務規則來移除錯誤，即每個錯誤根據偵測到的時間順序進行修復。但實際上，這些被偵測到的錯誤應該被歸類到不同的等級，優先權較高的錯誤要比優先權較低的錯誤更早被修復。
在本研究中，我們提出了一種同時考慮有限人力和不同優先權的佔先式優先權排隊模型。在此模型底下，優先權較高的錯誤將會佔先低優先權所佔據的資源。此了數學模型外，在此研究中我們也建構了一種以速率為基礎的模擬程序，此模擬程序能夠論證錯誤移除行為和評估佔先式優先權排隊模型的可靠度。我們提出的模擬程序可以深入研究錯誤移除過程，並且提供系統效能評估的資訊，如：人力配置、平均回應時間和平均等候時間。除了數學模型的建構，我們分析了來自開源軟體和閉源軟體的三個真實資料集。實驗結果發現，我們提出的數學模型和模擬方法都比傳統的軟體可靠度成長模型有更準確的可靠度估計能力。此外，我們所提出來的模型還可以提供資源分配的資料，可實際用於軟體專案管理上。我們預計該模型不僅可以為軟體開發管理提供有效的訊息，還可以幫助決策者進行資源分配和成本控制。

With the rapid development of technology, people are increasingly dependent on the services provided by many software in their daily lives. As the complexity and size of software grow, the requirement on software quality also become higher and higher. In previous published works, many software reliability growth models (SRGMs) have been successfully used to evaluate the quality of software. Some of those SRGMs have also shown that it is useful to model the fault detection process (FCP) and the fault correction process (FCP) through an infinite server queueing (ISQ) system or a finite server queueing (FSQ) system. However, most of the ISQ and FSQ models obey first come first served (FCFS) rule to remove those faults detected in FDP. In other words, those detected faults waiting for process are arranged in the order only based on the time serially. However, those detected faults should have been classified into different levels and those with higher priority should be served earlier.
In this study, we propose a preemptive priority queueing (PPQ) model that considers both finite debuggers and different priority levels. In PPQ model, faults assigned with higher priority will preemptively grab those resources that have been occupied by lower priority faults. Besides mathematical model, we also construct a rate-based simulation procedure in our work. This procedure is able to demonstrate the behavior of FCP and assess the reliability of the proposed PPQ model. Our proposed simulation procedure can deeply investigate FCP and easily provide system performance information estimated based on the staffing level, the average response time and the average waiting time. In addition to model construction, numerical examples based on three real data sets from open and closed source software are also presented and analyzed. Consequently, experimental results show that the proposed PPQ model and the simulation procedure can provide more accurate estimation capability of software reliability growth, compared to traditional SRGMs. Besides, the proposed PPQ model can also provide information of resource allocation for software project management in practice. We expect that PPQ model can not only provide effective information for software developing management but also help decision makers in resource allocation and cost control.

Chapter 1 Introduction 1
Chapter 2 Related works 5
2.1 Overview of SRGMs 5
2.2 The Concept of Queueing Theory 12
2.3 Simulation-Based Approaches 14
Chapter 3 Preemptive Priority Queueing Model 18
3.1 The proposed PPQ Model 18
3.2 Performance and Measurement of the PPQ Model 25
Chapter 4 Simulation Procedures with the Queueing Theoretic Approach 29
4.1 Procedure #1: The Simulation Procedure of Non-Preemptive Priority System 30
4.2 Procedure #2: The Simulation Procedure of Preemptive Priority System 35
Chapter 5 Numerical Examples 40
5.1 Selected data sets 40
5.2 Curve Fitting with Failure Data 47
 Least Square Estimation 47
 Maximum Likelihood Estimation 48
5.3 Criteria for Model Comparison 50
5.4 Case Study - DS1 54
5.5 Case Study - DS2 70
5.6 Case Study - DS3 84
5.7 Threats to Validity 98
Chapter 6 PPQ model Application for Software Project Management and Case Tool 101
6.1 The Efficiency of Correcting Faults 101
6.2 The response time of each fault 102
6.3 Resource Allocation Analysis for Staffing Levels 104
6.4 Reliability Visualization Simulator 110
Chapter 7 Conclusions 113
References 115
Appendixes 120

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