Database and Expert System Technology - Information Systems Reengineering, Integration and Normalization - page 38

RECORD NAME IS DEPARTMENT WITHIN ANY AREA

KEY DEPARTMENTID IS DEPARTMENT#

DUPLICATES ARE NOT ALLOWED

CALL CHECK-AUTHORIZATION BEFORE DELETE

DEPARTMENT# TYPE IS NUMERIC INTEGER

DEPARTMENT-NAME TYPE IS CHARACTER 30

RECORD NAME IS INSTRUCTOR WITHIN ANY AREA

KEY INSTRUCTORID IS INSTRUCTOR-NAME

DUPLICATES ARE ALLOWED

CALL CHECK-AUTHORIZATION BEFORE DELETE

INSTRUCTOR-NAME TYPE IS CHARACTER 30

INSTRUCTOR-ADDRESS TYPE IS CHARACTER 40

SET NAME IS HIRE
OWNER IS DEPARTMENT
ORDER IS PERMANENT INSERTION IS FIRST
MEMBER IS INSTRUCTOR
INSERTION IS AUTOMATIC RETENTION IS MANDATORY
SET SELECTION IS THRU HIRE OWNER IS IDENTIFIED
BY APPLICATION

The INSERTION clause specifies the class of membership of a member record in
a set type. There are two options in this clause, AUTOMATIC and MANUAL. For
the AUTOMATIC option, the system ensures the status of the member record in the
occurrences of the set type. For the MANUAL option, the application must handle
the record as a member of some set occurrence in the database. The RETENTION is
concerned with the ways in which records retain their membership in the database.
There are three ways; FIXED, MANDATORY, and OPTIONAL, for handling set
membership. For the FIXED option, if a record occurrence is made a member in
a set, then that record must exist as a member of the set in which it associates. For
MANDATORY, if a record is made a member in some set, then it must exist as a
member of some occurrence of this set type. Therefore, it is possible to transfer the
record from one set occurrence to another. For OPTIONAL, a record is allowed to
be moved from a set occurrence without requiring that the record be placed in a
different occurrence.

2.2.1 Network Data Definition Language

As shown in Fig. 2.4 , the database task group (DBTG) specification proposes three
levels of data organization. There are two pairs of Data Definition Language (DDL)