Understanding Properties of Dynamically Evolving Objects andTheir Schemas in Object Oriented Databases

面向对象的数据库旨在支持非传统数据库应用领域，如人工智能(AI)、计算机辅助设计(CAD)和办公信息系统(OIS)。非传统数据库应用的一个重要需求是支持应用演化，包括模式的演化和对象的演化。这项研究的总体目标是了解动态演化对象的属性及其模式，并在面向对象的数据库中找到支持它们的机制。本研究的目标之一是实现一个扩展的模式管理器，该管理器具有许多有用的动态模式管理功能，如模式演化、图形模式编辑器、模式版本控制、DAG重排视图和逻辑数据库模式设计。此外，本研究还将研究与动态模式管理密切相关的两个问题：(1)存储模型问题(即动态对象实例的存储方式)；(2)如何在动态模式变化的情况下实现代码(即方法)兼容的问题。本研究的贡献在于：(1)识别支持动态模式和对象所必需的数据结构和操作；(2)分析存储模型的基本性质；(3)研究面向对象数据库中能够应对动态模式变化的方法转换技术。

Object-oriented databases intend to support non-traditional database application areas such as artificial intelligence (AI), computer-aided design (CAD), and office information systems (OIS). An important requirement of non-traditional database applications is the support of application evolution which includes evolution of schemas as well as objects. The overall goal of this research is to understand properties of dynamically evolving objects and their schemas and find mechanisms for supporting them in object-oriented databases. One goal of this research is to implement an extensive schema manager having many useful capabilities for dynamic schema management, such as schema evolution, graphics schema editor, schema versioning, DAG rearrangement views, and logical database schema design. Also, in this research, two more issues which are closely related with dynamic schema management will be investigated: (1) storage model issue (i.e., ways of storing dynamic object instances), (2) the issue of how to achieve code (i.e., method) compatibility in the face of dynamic schema changes. This research contributes toward: (1) identifying data structures and operations which are necessary to support dynamic schemas and objects, (2) analyzing basic properties of storage models, and (3) investigating techniques for method conversion which can cope with dynamic schema changes, in object-oriented databases.