Data Modeling

Data Modeling - DataModeling ClicktoeditMastersubtitlestyle...

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Click to edit Master subtitle style  11/2/09 Data Modeling OPIM 3103 Section1 Fall 2009 Dmitry Zhdanov
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 11/2/09 More details on keys Basic data modeling notation Drawing Entity-Relationship diagrams Topics for today
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 11/2/09 Identify business requirements for the database Identify important objects (entities) Identify how entities are connected (relationships) Decide on the degree of participation of entities in  relationships Process of data modeling
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 11/2/09 An entity is an object about which we want to have  information in the database May be physical (e.g., person, car, building) May be conceptual (e.g., company, course, TV show) Entities are described by attributes What is an entity?
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 11/2/09 Types of Attributes Simple versus Composite Single-valued versus Multivalued Stored versus Derived
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 11/2/09 Simple versus Composite  Simple attributes are not divisible Example: SSN (Social Security Number), ID number Composite attributes can be divided into smaller  subparts which represent more basic attributes  with independent meaning. Example: Address It is a good idea to break up composite attributes  into simple parts (that makes for less work in 
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 11/2/09  Single-Valued versus  Attributes with a single value are referred to as  single-valued Example: Home Department (Finance Department) Multi-valued attributes – one or more entity  instances has more than one value for a specific  attribute Example: Phone (Cell number, House number, Work  number, etc.)
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 11/2/09 Stored versus Derived  Stored attributes become fields in resulting  tables Derived attributes can be calculated from related  attributes (in same or other entities) and will not  be stored in a table  Age - should be derived from DOB as it is time  dependent and is subject to change
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Data Modeling - DataModeling ClicktoeditMastersubtitlestyle...

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