The Object Definition Language

The EYEDB Object Definition Language (ODL) is a specification language to define the specifications of object types based on the ODMG ODL.
ODL ¹ is not intented to be a full programming language. It is a definition language for object specifications. Database management systems traditionaly provide facilities that support data definition (using a Data Definition Language (DDL)). The DDL allows users to define their data types and interfaces while the Data Manipulation Languages (DML) allows to create, delete, read update instances of those data types.
ODL is a DDL for objects types. If defines the characteristics of types, including their properties and operations. ODL defines only the signatures of operations and does not address definitions of the methods that implements those operations.
ODL is intented to define object types that can be implemented in a variety of programming languages. Therefore, ODL is not tied to the syntax of a particular programming language.

EYEDB ODL differs from ODMG ODL from several points:

• ODMG ODL defines class attributes, relationships, method signatures and keys. It supports nested classes, typedef constructs, constant definitions and exception hints.
• EYEDB ODL defines class attributes, relationships, method signatures, attribute constraints (notnull, unique, collection cardinality), index specifications and trigger declarations. It does not support nested classes, typedef constructs, constant definitions and exception hints.
• in EYEDB ODL, any type instance can be both a literal or an object. In ODMG ODL, this property is tied to the type: all basic types and user defined struct are literal while interfaces and classes are objects. In EYEDB ODL, any type instance can be an object, even the basic types.
• at last, EYEDB ODL allows to specify whether a method is backend or frontend, and whether it is a class or instance method.