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Database Modeling & Design Fourth Edition- P20

Database Modeling & Design Fourth Edition- P20: Database technology has evolved rapidly in the three decades since the rise and eventual dominance of relational database systems. While many specialized database systems (object-oriented, spatial, multimedia, etc.) have found substantial user communities in the science and engineering fields, relational systems remain the dominant database technology for business enterprises. | 82 CHAPTER 4 Requirements Analysis and Conceptual Data Modeling ships and process-to-data relationships. The conceptual data modeling step ER approach involves the classification of entities and attributes first then the identification of generalization hierarchies and other abstractions and finally the definition of all relationships among entities. Relationships may be binary the most common ternary and higher-level n-ary. Data modeling of individual requirements typically involves creating a different view for each end user s requirements. Then the designer must integrate those views into a global schema so that the entire database is pictured as an integrated whole. This helps to eliminate needless redundancy such elimination is particularly important in logical design. Controlled redundancy can be created later at the physical design level to enhance database performance. Finally an entity cluster is a grouping of entities and their corresponding relationships into a higher-level abstract object. Clustering promotes the simplicity that is vital for fast end-user comprehension. In the next chapter we take the global schema produced from the conceptual data modeling and view integration steps and we transform it into SQL tables. The SQL format is the end product of logical design which is still independent of any particular database management system. 4.7 Literature Summary Conceptual data modeling is defined in Tsichritzis and Lochovsky 1982 Brodie Mylopoulos and Schmidt 1984 Nijssen and Halpin 1989 Batini Ceri and Navathe 1992 . Discussion of the requirements data collection process can be found in Martin 1982 Teorey and Fry 1982 and Yao 1985 . View integration has progressed from a representation tool Smith and Smith 1977 to heuristic algorithms Batini Len-zerini and Navathe 1986 Elmasri and Navathe 2003 . These algorithms are typically interactive allowing the database designer to make decisions based on suggested alternative integration actions. A variety .