Wen-Wei Pan and Wei-Pang Yang
Department of Computer and Information Science
National Chiao Tung University
Hsinchu, Taiwan 300, R.O.C.
EODB is an object-oriented database currently being developed at the National Chiao Tung University. It intends to provide an easy-to-use inquiring system as well as a database kernel that can efficiently manage objects and classes. Two new ideas are proposed and implemented in EODB. First, it has a visual query language, Easy Query Language (EQL), that allows users to express queries directly using whatever knowledge they have without knowing the database schema. EQL can greatly alleviate the pains of remembering or browsing through a complex database schema when making queries. The EQL naming mechanism and four levels of EQL query resolution are proposed to bridge knowledge gaps between EQL queries and database schema.
Secondly, a new approach of managing classes and objects is implemented in EODB, the view classes and real-world objects model (V-R model). It is an object model 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. Further-more, view 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.
Keywords: object-oriented databases, object-oriented data models, object-oriented query language, object-oriented query optimization
Received September 27, 1995; revised July 12, 1996.
Communicated by Y.-S. Kuo.