network_model

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

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

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