功能分解式物件導向設計方法與環境設計

Abstract

本論文延續FDOOA方法之研究，提出其物件導向設計方法--FDOOD，並據 此探討物件導向軟體架構品質之量測方法以及物件導向軟體架構再利用之 程序。 FDOOD方法以FDOOA產出的類別模型為初步架構，定義實行類 別(implementation classes) 及其關係以得出完整的軟體架構，進而描 述各物件的生成與銷毀時機及其之間的交互引用關係，並對各類別進行細 部設計，得出各類別屬性的型別格式、運作及建構元/解構元之界面與演 算法。最後並進行系統初始化程序的設計。 在物件導向軟體架構品質量 測方面，本論文以類別架構為基礎，分別對構成類別架構的類別及類別關 係提出新的量測方法。在類別方面，以運作與屬性之使用關係所形成的語 意網路(semantic network)為依據，計算任兩運作及任兩屬性之間的最短 路徑之平均值，用以定義類別之內聚力(cohesion)；在類別關係方面，依 據類別關係的性質，將類別之間的耦合力(coupling)分成繼承式耦合及使 用式耦合兩大類，並考量兩類別互相影響的情形繼續將耦合力細分。最後 我們分析所提的內聚力及耦合力量測方法，提供一組修改設計的準則讓設 計師據此修改設計，並將此程序併入FDOOD方法中。 在物件導向軟體架 構再利用方面，是以新系統在分析階段所產生的類別模型為依據，在規格 儲存庫中尋找具有相似之類別模型的系統來做再利用。由於類別模型是由 類別及其之間的關係所組成的，故可以類別及類別關係當作比對之對象， 透過比對吻合的類別及關係在整個類別模型中所佔之比率，計算各系統與 當作相似度計算的依據，並依此結果將各系統依相似度高低列出，供設計 師一一檢視其內容以找出可再利用之類別及關係。最後，依各可再利用類 別與所需類別之差異情形進行修改，並進行組裝的工作。 另外，本論文 在IBM PC╱Windows 95上發展一套FDOOD輔助環境，提供設計師建立FDOOD 設計規格及搜尋/檢視現有設計規格之再利用環境，此環境已以C語言及物 件導向資料庫製作完成。 The ObjeCtives of this research is to propose : (1)an object- oriented design method, FDOOD method, based on the result of FDOOA method (2)new metrics to measure the cohesion and coupling of classes, and (3)an approach to reuse the architecture of object-oriented software. The major procedures of FDOOD includes (1)defining the implement classes and their relationship based on the class model which consists of all domain-specific classes of the problem. (2)defining when each object should be constructed/destructed, (3)defining data type for each attribute of class, and (4)designing the algorithm for each operation of the class. To measure the quality of architecture of object-oriented software, this thesis proposes to measure the complexity the software architecture, the cohesion of each class, and the coupling of classes. Since the available cohesion and coupling metrics have some shortages, this thesis propose two metrics of measure the cohesion and coupling of classes. To measure the cohesion of a class, the semantic network of the class is constructed first. The cohesion of a class can be computed from the shortest paths of each two operations and each two attributes. Coupling between classes can be classified as inheritance-coupling and use-coupling. Two metrics to measure inheritance-coupling and use-coupling are proposed. For the reuse of software architecture, we propose to use the domain-specific classes and their relationship produced in the analysis stage to retrieve the similar reusable architecture for reuse. The formula to compute the similarity of reusable architecture is designed. The designer should examine the content of the retrieved architecture to verify their suitability. The reuse procedure has been incorporated into the FDOOD method. An FDOOD environment on IBM PC with Windows 95 is designed, and implemented with C language and APOC Object-Oriented Database Management System.