A Data Base Schema contains description of all data types which are of interest to users. A Data Base contains instances of data types previously defined in a current Data Base Schema. A Data Base Schema is a list of existing files. Whenever a user creates a new file its description is automatically added to the data base schema.
Domain is a column of relation.
Domain is a subset of a relation's column. Domain includes a column of relation. Relational DBMS must maintain both the Entity Integrity and Referential Integrity independent of a concrete application. Users are responsible for maintaining both the Entity Integrity and Referential Integrity. Users may define the Entity Integrity or Referential Integrity in a corresponding data base schema.