Basic Terms

While relational and object databases use different sets of terms, it is possible to draw parallels between some of the terms:

OODBMS

RDBMS

Similar

Different

Class

Table

Define an entity data structure.

Class can define fields (static data) and methods, while table can only define static data.

Object instance

Tuple

Represent an instance of data defined in a class or a table.

Object can hold data of different visibility and references to other objects. Tuple consists of system type data.

Attribute

Column

Define one of the fields in the data definition.

RDBMS has a preset collection of types, which can be used to define the type of the data in the column. OODBMS can use user-defined types.

Method

Stored Procedure

Define a piece of functionality.

Method is a characteristic of a class. Stored procedure is a separate object in RDBMS.

Identity

Key

Identify a single object or tuple.

Object identity makes any object unique independently of the object content. Key imposes a uniqueness of a database object based on the uniqueness of the column values.

Reference

Relation

Link different objects within a database.

In OODBMS direct object links are used. In RDBMS objects are linked through foreign keys, i.e. identical values in different rows.

Note, that the above-mentioned terms are similar only to a certain degree; there are some fundamental differences between them.