The NDBMS is built primarily on a one–to-many relationship, but where a parent-child representation among the data items cannot be ensured. This may happen in any real world situation where any entity can be linked to any entity. The NDBMS was proposed by a group of theorists known as the Database Task Group (DBTG). What they said looks like this:
In NDBMS, all entities are called Records and all relationships are called Sets. The record from where the relationship starts is called the Owner Record and where it ends is called Member Record. The relationship or set is strictly one-to-many.
In case we need to represent a many-to-many relationship, an interesting thing happens. In NDBMS, Owner and Member can only have one-to-many relationship. We have to introduce a third common record with which both the Owner and Member can have one-to-many relationship. Using this common record, the Owner and Member can be linked by a many-to-many relationship.
Suppose we have to represent the statement Teachers teach students. We have to introduce a third record, suppose CLASS to which both teacher and the student can have a many-to-many relationship. Using the class in the middle, teacher and student can be linked to a virtual many-to-many relationship.
