Abstract Concepts

[quenio]

Abstract concepts are only inherited and they are never instantiated directly. They may also contain derived attributes whose definition is deferred to the sub-classes.

In CML, a concept may be defined as abstract by using the "abstract" keyword before the "concept" keyword.

During code generation, no code needs to be generated to allow their direct instantiation of abstract concepts by clients.

Acceptance criteria:

• The "abstract" keyword can be used in CML before the "concept" keyword to define a concept as abstract.
• In the CMLC target, the abstract concepts will have create methods and constructors that accept the instances representing the inherited classes as parameters. Concrete concepts will instead instantiate the base classes in the constructor.
• In the POJ target, the abstract concepts will be declared as abstract. The ancestors will be just inherited.