Information Technology Reference
In-Depth Information
Nonrelational schema
Modified "open" sc hema
CUSTOMER
(F)
CUSTOMER
(F)
Cust omer#
Cust omer#
IX
Cust omer#
LOAN
(P)
LOAN
(P)
Loan#
Loan#
IX
Cust omer#
COLLATERAL
(I)
COLLATERAL
(I)
Loan#
Sequence#
Fig. 5.5 Add derived secondary indices
Network
Schema
Network
Database
Pre-process
step 1
Virtual
translated
relational
schema
Pre-process
step 2
Schema
translation
Add secondary
indices
Relational Interface
Transparent to
users as
relational schema
"open"
schema
Network
Database
+
Secondary
indice
Network
Schema
+
Secondary
Indice
Step 1
program
conversion
Embedded
SQL
Programs
End-User
Step 2
Network
DBMS
Process
Converted
Network
Programs
Fig. 5.6 Relational interface provision for network databases
Preprocess step 1. Map network schema to a relational schema and derive sec-
ondary indices.
We first map the original network schema into a corresponding relational schema
by
 
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