設計與製作一個容易使用且高效率的物件導向式資料庫（EODB）

Abstract

EODB為在國立交通大學資訊科學研究所發展物件導向資料庫，它的目的在 於提供一個容易使用且高效率的物件導向資料庫。為此，兩個首創的新觀 念是EQL和V-R Model。EQL為一個非常易於使用的物件導向查詢語言，其 第一個主要的想法是允許使用者以其僅有的常識來使用查詢語言，而無須 事先知道一個資料庫的綱要；第二個主要的想法是提供使用者一個優良的 互動式查詢環境。為完成第一個目標，我們提出EQL的命名機制與EQL的查 詢決議法，以解決當使用者依常識下達的查詢與資料庫的綱要有異時的問 題。為完成第二個目標，我們製作了一個能依使用者的行為，自動地顯示 使用者可能會有興趣的部份綱要。V-R Model定義了一個抽象的物件導向 資料庫核心模型，其主要功能在於提供一個非常有效率、支援可更新的資 料庫景觀機制，V-R Model設計了一種特別的方法去描述物件與類別的關 係，允許一個物件可同時屬於多個類別。利用此特性與V-R Model的封閉 性，查詢結果便可以非常有效率地被管理，且無須複製任何物件的資料。 如此，可更新的資料庫景觀機制便可容易地達成。此外、我們以V-R Model為基礎，更進一步地釐清，因物件導向資料模型的特質而使得景觀 機制更新意義之模糊處。此外，我們也探討了我們所製作的EODB系統中， 數個重要的製作關鍵技術。 EODB is an object-oriented database developed at the National Chiao Tung University. It intends to be an easy-to-use and efficient object-oriented database system. Two new ideas are proposed to implement EODB. First, Easy Query Language (EQL) is a query language designed to provide users an easy-to-use inquiry tool. One approach to achieving this goal is to allow users to express queries directly with whatever knowledge they have, and without knowing the database schema. The other approach is to give users an interactive inquiry environment in which to build queries. Pursuing the first approach, we propose an EQL naming mechanism and four levels of EQL query resolution that serve to bridge knowledge gaps between EQL queries and database schema. Pursuing the second approach, our EQL user interface is designed to automatically provide helpful information to users constructing queries.Secondly, the model of view classes and real-world objects (V-R model) is a model of database's kernel at the conceptual level of abstraction. The major goal of the V-R model is to support updatable views efficiently for the object-oriented database systems. The V-R model elaborates a special method to describe the instance-of relationship between stored objects and classes, so that a stored object can be the instance of several classes simultaneously. Query results and views can be managed like classes without creating temporary objects or tuples, since the V-R model is closed against query operations. In this way, updates on views can be supported easily. Besides, the update semantics is explored in depth. Based on the V-R model, a more eligible translation is proposed for the updates on classes with or without inheritance relationships and for the updates on views. Several implementation techniques about EODB are discussed too.