Technical data

Figure 5–5 Sample Occurrence Diagram 2
LABEL
4−DAYS
SOUND−OFF CO
CASSETTE
2−WEEKS
2−DAYS
1−MONTH
1−WEEK 5−DAYSMUSICO, INC.
PART_INFO SET
VENDOR_SUPPLY SET
VENDOR RECORD TYPE
PART RECORD TYPE
SUPPLY RECORD TYPE
TAPE
ZK−1483−GE
5.9 Sets
Sets are the basic structural units of a database. A set occurrence has one
owner record occurrence and zero, one, or several member record occurrences.
Figure 5–6 shows one occurrence of PART_SUPPLY set where PART A owner
record occurrence owns two SUPPLY member record occurrences.
Set types establish a logical relationship between two or more types of records. A
subschema usually includes one or more set types. Each set type has one record
type that participates as the owner record and one or more record types that
participate as members. These owner and member records are grouped into set
occurrences.
Database Programming with HP COBOL 5–9