What is Relationship type?
Relationship type defines a set of associations or a relationship set among a given set of entity types.

What is degree of Relationship type?
It is the number of entity type participating.

What is DDL (Data Definition Language)?
A data base schema is specifies by a set of definitions expressed by a special language called DDL.

What is VDL (View Definition Language)?
It specifies user views and their mappings to the conceptual schema.

What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This language may specify the mapping between two schemas.