Schema Translation - Information Systems Reengineering, Integration and Normalization - page 91

5HFRUGLGHQWLILHU
&XVWRPHU

&XVWRPHU

&XVWRPHU

&XVWRPHU

VHW

5HFRUGLGHQWLILHU
/RDQ

/RDQ

/RDQ

/RDQ

VHW

5HFRUGLGHQWLILHU
&ROODWHUDO

&ROODWHUDO

&ROODWHUDO

&ROODWHUDO

Fig. 3.13 Map network schema with fully internally identifier to relational

5HFRUGLGHQWLILHU
&XVWRPHU

&XVWRPHU &XVWRPHU

&XVWRPHU

VHW

5HFRUGLGHQWLILHU
&XVWRPHU
/RDQ

/RDQ /RDQ

/RDQ

VHW

5HFRUGLGHQWLILHU
&XVWRPHU
/RDQ
&ROODWHUDO

&ROODWHUDO

&ROODWHUDO

&ROODWHUDO

Fig. 3.14 Map network schema with partially internally identifier to relational

• Partiallyinternallyidentified—Concatenationofownerrecord(s)key(s)withthe
member record key can uniquely identify the member record (i.e., identifier de-
pendency). For example, the same loan system records could be identified as in
Fig. 3.14 . Here Loan# is only unique within a customer and Collateral# is only
unique within a loan.
• Internallyunidentified—Therecordkeydoesnotexist. Some other property (such
as ordering) may be used to impart an implicit internal identifier. This is an ex-
treme case of a partially internally identified group for which an augmented identi-
fier consists solely of external identifiers. For example, in the same loan system,
the Collateral record may not have a key. Its record identifiers must then be derived
as in Fig. 3.15 . Here Sequence# is added as an additional field for the identifier.