network_model

network_model - NETWORK MODEL (CO Dasyl Model DBTG Model)...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
NETWORK MODEL (CO Dasyl Model – DBTG Model) CODASYL : Conference on Data System Language. DBTG : Database Task Group. Data-item DEPTT NAME, etc. Record DEPTT, FACULTY STUDENT Set APPOINTMENT, MAJOR, ADV. Set-member FACULTY, STUDENT, STUDY Set-owner DEPTT, DEPTT, FACULTY FACULTY STUDENT owner owner owner member member member APPOINTMENT MAJOR DN ADVISOR DEPARTMENT WARD DOCTOR PATIENT OCCUPANCY ATTENDING DOCTOR
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Characteristics of a SET 1. A set is a collection of records. 2. Each set has one owner record type and one or more member record types. 3. Each owner record occurrence defines a set occurrence. 4. A record may be a member of more than one set type. 5. A record may not be a member of two occurrences of the same set type. 6. A record may not be a member and an owner of the same set type. 7. A record may own more than one set. Many – Many relationships cannot be represented in DBTG set concepts. Solution
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 5

network_model - NETWORK MODEL (CO Dasyl Model DBTG Model)...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online