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Chapter+8+-+1 - Data Modeling and Analysis Chapter 8 Data...

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Data Modeling and Analysis Chapter 8
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Data Modeling Technique for organizing and documenting a system’s data. Sometimes called database modeling . Entity Relationship Diagram (ERD) – Data Model utilizing several notations to depict data in terms of the entities and relationships described by that data.
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Sample Entity Relationship Diagram (ERD)
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T Persons : agency, contractor, customer, department, division, employee, instructor, student, supplier. e Places : sales region, building, room, branch office, campus. e Objects : book, machine, part, product, raw material, software license, software package, tool, vehicle model, vehicle. e Events : application, award, cancellation, class, flight, invoice, order, registration, renewal, requisition, reservation, sale, trip. e Concepts : account, block of time, bond, course, fund, qualification, stock. Entities A class of persons, places, objects, events, or concepts about which we need to capture and store data. Named by a singular noun.
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Entities (Continued) Entity instance – a single occurrence of an entity. Student ID Last Name First Name 2144 Arnold Betty 3122 Taylor John 3843 Simmons Lisa 9844 Macy Bill 2837 Leath Heather 2293 Wrench Tim instances entity
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Attributes Descriptive Property or Characteristic of an Entity. Synonyms include element , property , and field . Just as a physical student can have attributes, such as hair color, height, etc., a data entity has data attributes. Compound Attribute – an Attribute that consists of other Attributes. Synonyms in different data modeling languages are numerous: concatenated attribute, composite attribute, and data structure.
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Data Type Property of an Attribute that identifies what type of data can be stored in that Attribute. Representative Logical Data Types for Attributes
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Chapter+8+-+1 - Data Modeling and Analysis Chapter 8 Data...

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