aChapter 15 - Overview The design process in multidatabase...

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Overview •T h e d e s i g n p r o c e s s i n multidatabase systems is bottom-up. – The individual databases actually exists – Designing the global conceptual schema (GCS) involves integrating these local databases into a multidatabase. Database integration can occur in two steps: Schema Translation and Schema Integration . Database 1 Database 2 Database 3 Translator 1 Translator 2 Translator 3 InS 1 Intermediate schema in canonical representation InS 2 InS 3 INTEGRATOR GCS
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Network Data Model (Review) There are two basic data structures in the network model: records and sets . DEPARTMENT (DEPT-NAME, BUDGET, MANAGER) EMPLOYEE (E#, NAME, ADDRESS, TITLE, SALARY) Record type : a group of records of the same type. Set type : indicates a many-to-one relationship in the direction of the arrow. Representation of set instances: Employs owner record type set type member record type Database Jones, L. Patel, J. Vu, K. DEPARTMENT (owner record) STUDENT (member records)
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Example: Three Local Databases Database 1 (Relational Model): S (TITLE , SAL) E (ENO , ENAME, TITLE) J (JNO , JNAME, BUDGET, LOC, CNAME) G (ENO, JNO , RESP, DUR) Database 2 (Network Model): DEPARTMENT (DEPT_NAME, BUDGET, MANAGER) EMPLOYEE (E#, NAME, ADDRESS, TITLE, SALARY) Employs
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Example: Three Local Databases Database 3 (ER Model): Project No. Project Name Responsibility Engineer No. Engineer Name Title Salary Budget Location Duration Contract Date CONTRACTED BY CLIENT 1 Address Client Name ENGINEER WORKS IN N PROJECT 1 N
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Schema Translation: Relational to ER S (TITLE , SAL) E (ENO , ENAME, TITLE) J (JNO , JNAME, BUDGET, LOC, CNAME) G (ENO, JNO , RESP, DUR) ENO TITLE SAL E PAY S NM N 1 From our knowledge of the semantics of the database, we know E & J have a many-to-many relationship. JNO JNAME ENAME RESP J G CNAME DUR LOC BUDGET Treat salary as an attribute of an engineer entity JNO JNAME ENO ENAME RESP E J TITLE SAL CNAME LOC BUDGET DUR Relationships may be identified from the foreign keys defined for each relation.
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Schema Translation: Network to ER WORK DEPARTMENT EMPLOYEE Map each record type in the network schema to an entity and each set type to a relationship. Network model uses dummy records in its representation of many-to-many relationships that need to be recognized during mapping. WORK Employs Works-in DEPARTMENT EMPLOYEE EMPLOYS WORKS-IN 1 1 N N DEPARTMENT EMPLOYEE EMPLOYS NM
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Schema Integration Schema integration follows the translation process and generates the GCS by integrating the intermediate schemas. – Identify the components of a database which are related to one another. • Two components can be related as equivalent, one contained in the other one, overlapped, or disjoint. – Select the best representation for the GCS. – Integrate the components of each intermediate schema.
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Integration Methodologies Integration Proces Binary: Decreases the potential integration complexity and lead toward automation techniques.
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This note was uploaded on 12/23/2009 for the course DBST 663 taught by Professor Tba during the Spring '09 term at MD University College.

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aChapter 15 - Overview The design process in multidatabase...

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