Chapter 14 INFORMAL DESIGN GUIDELINES FOR RELATION SCHEMAS FOUR INFORMAL MEASURES: 1. Semantics of Attributes. 2. Reducing redundant values in TUPLES. 3. Reducing Null values in TUPLES. 4. Disallowing possibility of Generating Spurious Tuples DOC

Title	Chapter 14 INFORMAL DESIGN GUIDELINES FOR RELATION SCHEMAS FOUR INFORMAL MEASURES: 1. Semantics of Attributes. 2. Reducing redundant values in TUPLES. 3. Reducing Null values in TUPLES. 4. Disallowing possibility of Generating Spurious Tuples
Author	Sharans Kumar
Pages	43
File Size	1.7 MB
File Type	DOC
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Chapter 14 INFORMAL DESIGN GUIDELINES FOR RELATION SCHEMAS FOUR INFORMAL MEASURES: 1. Semantics of Attributes. 2. Reducing redundant values in TUPLES. 3. Reducing Null values in TUPLES. 4. Disallowing possibility of Generating Spurious Tuples. 1. SEMANTICS OF ATTRIBUTES: Whenever we group attributes to form relation, We assume certain meaning associated with attributes. This meaning we call "SEMANTICS". It tells how to interpret the values stored. Easier the semantics, better the relation schema would be. Guideline 1 Design relation schema so that it is easy to explain the meaning. Do not combine attributes from multiple entity types into single relation. Note: A relation schema should always correspond to one entity type or one relationship type, for the meaning to be clear. Refer fig 10.3 for bad relation schema design. Combines two entities into one schema. 1. Reducing redundant values in TUPLES.: If Redundant values are not reduced.. We face the following problems. Redundant information increases storage space. Redundant information in Tuples introduces "UPDATE ANAMOLIES"....