Abstract: A database management system is disclosed having an object oriented representation of information describing characteristics of instances organized in a hierarchical structure that may be logically represented as a tree structure. The hierarchical structure includes a parent-child/class-subclass structure. The internal representation of an instance is dependent upon information that is locally available from a class to which that instance belongs plus inherited attributes from a parent class. A class is represented as a class object having a handle. The class object has a parent handle associated with it that identifies the parent class of the class object. The class object has a subclass list associated with it that identifies the handles of the classes that are subclasses of the class object. The class object has an attribute list associated with it that includes a list of handles which may be used to identify the attributes of the class object.

Abstract: The present invention is an improvement upon an object oriented database management system and provides a method and apparatus for a user to visually compare attribute values of instances retrieved in a search in a way that highlights attribute values that do not match or are not equal. The present invention provides a method and apparatus for determining which of the attributes are not equal or do not match, and which attribute values are the same for all of the instances that are retrieved by a search. A method and apparatus is provided for visually indicating such determinations in a way that is immediately understandable by a user.

Abstract: The present invention provides a method and apparatus for concurrency control in an object oriented database management system having a plurality of users accessing the system at the same time, and allowing editing of the database while other users are concurrently searching the database. The present invention may be advantageously used in a client/server architecture comprising a knowledge base client and a knowledge base server. In a preferred embodiment, the knowledge base server may include an object oriented lock manager, a dynamic class manager, a connection manager, a query manager, a handle manager, a units manager, a database manager, and a file manager. The concurrency control mechanism includes a lock holder table. The present invention provides a method and apparatus for providing concurrency control in an object oriented database managemant system using only three types of lock modes: a class share lock, a tree update lock, and a tree exclusive lock.