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Lecture Database Systems - Lecture 19

After completing this chapter, students will be able to: SQL development: an overview; DDL: create, alter, drop; DML: select, insert, update, delete; DCL: commit, rollback, grant, revoke; assertions; triggers; views. | CSC271 Database Systems Lecture # 19 Summary: Previous Lecture Information system Database System Development Life Cycle Database planning System definition Requirements collection and analysis (To be continued ) Requirements Collection and Analysis Another important activity is deciding how to manage the requirements for a database system with multiple user views Three main approaches Centralized approach View integration approach Combination of both approaches (Hybrid) Centralized Approach Requirements for each user view are merged into a single set of requirements A data model is created representing all user views during the database design stage Centralized Approach View Integration Approach Requirements for each user view remain as separate lists Data models representing each user view are created and then merged later during the database design stage View Integration Approach Local/Global data models Data model representing single user view (or a subset of all user views) is called a local data model Each model includes diagrams and documentation describing requirements for one or more but not all user views of database Local data models are then merged at a later stage during database design to produce a global data model, which represents all user views for the database View Integration Approach Database Design Process of creating a design for a database that will support the enterprise’s mission statement and mission objectives for the required database system Main database design approaches include: Top-down Bottom-up Inside-out Mixed Data Modelling Main purposes of data modeling include: To assist in understanding the meaning (semantics) of the data To facilitate communication about the information requirements Building data model requires answering questions about entities, relationships, and attributes Data Modelling A data model ensures we understand: Each user’s perspective of the data Nature of the data itself, independent of its physical . | CSC271 Database Systems Lecture # 19 Summary: Previous Lecture Information system Database System Development Life Cycle Database planning System definition Requirements collection and analysis (To be continued ) Requirements Collection and Analysis Another important activity is deciding how to manage the requirements for a database system with multiple user views Three main approaches Centralized approach View integration approach Combination of both approaches (Hybrid) Centralized Approach Requirements for each user view are merged into a single set of requirements A data model is created representing all user views during the database design stage Centralized Approach View Integration Approach Requirements for each user view remain as separate lists Data models representing each user view are created and then merged later during the database design stage View Integration Approach Local/Global data models Data model representing single user view (or a subset of all user views) .