Data Definition Facilities in Admin

Admin is a database management system based on the network model of data. It has a number of data definition facilities over and above those provided by the CODASYL DDLC. It is possible to define a schema and build subschemas on top of it. Further, one can build another layer of subschemas on any given subschema, subject to the restriction that a total of 63 subschemas are built on top of any schema. It is also possible to define one's own value sets from which fields of records can take on values. Further, one can build 'new' corecs over currently existing corecs. Similarly, one can also define new cosets between any pair of corec types currently existing in a subschema. There is also an authorization and access control specification available with Admin. All these features are described herein.