軟體工程師在軟體維護階段 (Software Maintenance Phase) 要負責改變軟體以滿足改變的使用者需求以及修正軟體設計時所遺留的不完善處，軟體重構 (Software Refactoring) 可協助軟體工程師以不改變程式碼外在行為的前提下改進軟體的結構 (Software Structure)，適當的軟體重構可以幫助改變軟體結構使軟體更具可延伸性 (Extensibility) 以利進一步的改變。然而，軟體工程師在進行軟體重構時，往往不清楚特定重構對軟體結構的整體的影響，在缺乏得知重構對軟體結構影響的狀況下，軟體工程師往往在進行軟體重構時需以嘗試錯誤法反覆嘗試不同重構方法 (Refactoring Method)，導致軟體重構的程序 (Refactoring Process) 缺乏效率。本篇碩士論文提出了預覽 (Preview) 軟體重構對軟體結構影響的機制，軟體重構對軟體結構的影響以一組可以對映軟體結構改變的軟體量測改變 (Software Metrics Changes) 表示；為了從軟體重構中得知軟體量測改變，軟體重構所帶來的結構改變 (Structural Change) 會被拆解成「單元改變」 (Atomic Change)，並進一步由單元改變推導出軟體量測改變。本論文亦介紹了以基於上述機制所實作的軟體重構的工具：Refactoring Previewer，Refactoring Previewer 在軟體重構時所提供的軟體量測變量可以協助軟體工程師了解軟體重構對軟體結構的改變並進一步幫助軟體工程師以更有效率的方式在軟體重構程序中進行決策。

During software maintenance, software developers are responsible to change the software for fulfilling the change of user requirement and for fixing the design flaw. Software refactoring provides developers a behavior preserving way to enhance software structure. With proper refactoring, the refactored software would be more extendable for further change. However, during refactoring, the overall effect of refactoring on software structure is often unclear for the developer. The lack of information about the effect of refactoring makes the process of applying refactoring inefficient. In this work, a mechanism that provides developers to preview the refactoring effect is presented. The refactoring effect is represented as a set of software metrics that can reflect the structure of software. To assess the effect of refactoring, the structure changes made by refactoring is decomposed to a series of atomic changes. The effect of refactoring on software metrics is then induced from these atomic changes. A tool: Refactoring Previewer that helps developer preview refactoring effect is implemented. The metrics change information provides by Refactoring Previewer can help developer understand the refactoring impact on software structure and make refactoring decision in more efficient way.

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