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Data analysis and design, , wixom, and roth. © 2015 John Wiley & Sons. All Rights 1Learning Objectivesq Explain the rules and style guidelines for creating. entity relationship diagrams (ERDs)q Create an ERDq Describe the use of a data dictionary and. metadataq Explain how to balance ERDs and data flow. diagramsq Describe the process of normalization © 2015 John Wiley & Sons. All Rights 2 Key Definitionsq Data model. o A formal way of representing the data that are used and. created by a business system. o Shows the people, places and things about which data is. captured and the relationships among them o Logical data model shows the organization of data without. indicating how it is stored, created, or manipulated. o Physical data model shows how the data will actually be. stored in databases or files. © 2015 John Wiley & Sons. All Rights 3Key Entity Relationship Diagram (ERD). o A popular way to depict the data Normalization is the process analysts use to. validate data modelsq Data models should balance with process. models. © 2015 John Wiley & Sons. All Rights 4Why Is Data Modeling Crucial? q Data is a resource to be shared by as. many processes as possible q Data organization must be flexible and. adaptable to unanticipated business. requirements – and that is the purpose of. data modeling © 2015 John Wiley & Sons. All Rights 5Other Data Modeling Issues q Data structures and properties are reasonably. permanent –more stable than the processes that use. the dataq Typically very similar to the existing systemq Data models are much smaller than process models. and are constructed more rapidlyq Constructing the data model helps analysts and users. quickly reach consensus on business terminology and. rules. © 2015 John Wiley & Sons. All Rights 6Entity Relationship do erds tell us?. © 2015 John Wiley & Sons. All Rights ERD. © 2015 John Wiley & Sons. All Rights 8Using the ERD to Show Business rules are constraints that are followed when. the system is in operationq ERD symbols can show when one instance of an entity. must exist for an instance of another to exist. o The chemical must exist before chemical requests can be. created for that chemical. o The lawn chemical applicator must exist before chemical. requests can be created by that lawn chemical applicator © 2015 John Wiley & Sons. All Rights 9Using the ERD to Show , con’tq ERD symbols can show when one. instance of an entity can be related to. only one or to many instances of another. entity. o One LCA can create many chemical. requests; each chemical request is created. by only one LCA. o A chemical can be included on many. chemical requests; a chemical request is for. only one chemical Wiley & Sons. All Rights. © 2015 John 10Using the ERD to Show , con’tq ERD symbols show when the existence. of an entity instance is optional for a. related entity instance. o A chemical may exist without being included. on any chemical requests. © 2015 John Wiley & Sons. All Rights 11An ERD Example Entities. CUSTOMER has placed ORDER. Customer ID Order ID. Name Order Date. Address Order Total Cost. Telephone . © 2015 John Wiley & Sons. All Rights A person, place, event, or thing about. which data is Must b

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