this will take care of the association between a weak entity type and a strong

This will take care of the association between a weak

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this will take care of the association between a weak entity type and a strong entity type because you will add the PK of the strong entity type relation (the “1”) to the weak entity type relation (the “M”) Step 4: Break down composite attributes into their atomic parts: and then REMOVE those composite attributes (they should not appear in any logical schema relation) and re-enter them as a set of atomic attributes Step 5: In each relation, indicate which attribute or set of attributes is the PK by underlining it/them for relations created from entity types, mark the PK as indicated directly from the ER diagram for relations created from M:N (or higher) relationships, if the PK is not given to you by the end- users, the PK is the combination of the PKs of all associated entity types, or you can make up a PK (typically an incrementing integer) for relations created from multi-valued attributes, the PK is the PK of the original entity type PLUS the multi-valued attribute itself for relations created from weak entity types, the PK is the PK of the associated strong entity type PLUS the partial identifier of the weak entity type Step 6: Indicate all foreign keys by dashed underlining them you can’t do this in Word or PowerPoint using the font underlining tool; it’s irritating, but one solution is to add in the dashed underlining by hand after your diagram is printed (remember that an FK is just an attribute or set of attributes that is the PK of another relation) Indicate the PK that each FK is associated with draw a line from the FK to its associated PK with an arrow on the PK end of that line Your logical schema of relations is now complete!
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  • Spring '14
  • B MAK
  • Entity-relationship model, entity, entity type, IDEF1X

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