Review of Temporal Object-Oriented Approaches

Class. Abstract class is a class that has no instances. An abstract class is written with the expectation that its concrete subclasses will add to its structure and behaviour, typically by implementing its abstract operations. Extent. The extent of a type is the set of all instances of the type. Review of Temporal Object-Oriented Approaches Page 4 Object Equality. There are at least two different notions of equality between objects: . Identity equality: Two objects are identical if they are the same object, that is, if they have the same identity. . Value equality: Two objects are equal if the values of all their attributes are recursively equal. Keys. An attribute or a set of attributes whose value uniquely identifies a single target object. Schema Modification. A change to the database schema is called schema modification. Possible types of schema modifications in an object-oriented database include: Modifying the class definition by . Modifying attributes . Modifying meth..