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Database Design with Semantic Object Models

Database Design with Semantic Object Models. Mapping 7 types of semantic objects into relations. Simple objects. Transform object into relation Make ID into key Other attributes become columns. Composite objects. One relation for base object Include single-valued attributes

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Database Design with Semantic Object Models

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  1. Database Design with Semantic Object Models Mapping 7 types of semantic objects into relations

  2. Simple objects • Transform object into relation • Make ID into key • Other attributes become columns

  3. Composite objects • One relation for base object • Include single-valued attributes • One relation for each (simple or group) multi-valued attribute • Key of child relation is composite: • Foreign key of object • Local key of multi-valued attribute

  4. Separate versus nested groups • Iterate composite object procedure • Outer group is base object for inner group

  5. Compound objects • Basically 3 types of binary relationships

  6. Compound objects • 1:1 - place key of either table into other table

  7. Compound objects • 1:N - place key of parent into child table

  8. Compound objects • N:M - create intersection table with keys of both relations

  9. Hybrid objects • Create a table for the multi-valued group attribute of the composite object • Place key of non-composite object into that table SALES-ORDER (SalesOrderNumber, Date, Subtotal, Tax, Total, Phone, SalespersonName) ITEM (ItemNumber, ItemDescription, UnitPrice) LINE-ITEM (SalesOrderNumber,ItemNumber, Quantity, ExtendedPrice)

  10. Hybrid objects • Actually, 4 cases of hybrid objects

  11. Hybrid Object Max Cardinality • Case One • ITEM in one ORDER and only one LineItem

  12. Hybrid Object Max Cardinality • Case Two • ITEM in one or more LineItems within one SALES-ORDER

  13. Hybrid Object Max Cardinality • Case Three • ITEM in one LineItem within one SALES-ORDER

  14. Hybrid Object Max Cardinality • Case Four • ITEM in one or more LineItems within one SALES-ORDER

  15. Hybrid object common cases • Case 4: O3 is inserted into R-G2 but not as part of its local key • Case 1: like 3 but add O1 to R2 and R2(O1,O2) = R-G1(O1,O2) • Case 2: like 4 but add O1 to R3 and R-G2(O1,O3) Í R3(O1,O3)

  16. Association objects • One relation for each of the 3 participating objects • Each relation has its own key • Association relation has parents’ keys as foreign keys • If association has no unique ID, use foreign keys • Unlike intersection relations, association tables may have additional attributes

  17. Super/subtype objects • One table for parent • One table for each subtype • Normally same key for all • May add subtype attribute(s) to parent for efficiency • One label if exclusive • One Boolean per type, if not exclusive

  18. Archetype/version objects • One table for archetype • One table for version • Key of version table contains key of archetype table

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