final exam study guide 2

final exam study guide 2 - Chapter 7 Conceptual data...

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Chapter 7 Conceptual data modeling o Representation of organization data to show rules about the meaning and relationships between data, most commonly using ERD’s o 4 ERD’s produced during conceptual data modeling Data needed in project application ERD for system being replaced ERD for the whole database from which the new app data extracted ERD for the whole database from which data for app system being replaced are drawn o Gathering information – two ways Top down Data model is derived from an intimate understanding of the business Bottom up Data model is derived by reviewing specifications and business documents o Entity Person, place, object, event, or concept in the user environment o Entity type Collection of entities that share common properties o Entity instance Single occurrence of an entity type o Attribute Named property or characteristic of an entity o Candidate key Attribute or combination that uniquely identifies each instance of an entity type o Identifier Candidate key that has been selected as the unique identifying characteristic for an entity type Rules Not change its value Never be null No intelligent keys Use large composite keys when possible o Multivalued attribute Attribute that may take on more than one value for each entity instance Double lined ellipse or weak entity o Relationship Association between instances of one or more entity types Always labeled with verb phrases o Goal Capture as much of the meaning of the data as possible
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o Result A better design that is easier to maintain o Degree Number of entity types that participate in a relationship Unary o Between instances of one entity type Binary o Between instances of two entity types Ternary o Between instances of three entity types o Cardinality Number of instances of entity B that can be associated with each instance of entity A o Associative entity An entity type that associates instances of one or more other entity types and contains peculiar attributes to the relationship Chapter 8 Designing the human interface o Form Business document that contains some predefined data and may include some areas where additional data are to be filled in An instance of a form is typically based on one database record o Report Business document that is for reading or viewing and contains only predefined data, typically contains data from records or transactions o Prototyping Designed from requirements, then users review and either accept or request changes, if requested then a construction/evaluation/request cycle is repeated until design is accepted o Design specification deliverables Narrative overview, sample design, testing and usability assessment o Data errors Appending Adding additional characters to a field Truncating Losing characters from a field Transcripting Entering invalid data into a field
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This note was uploaded on 01/10/2012 for the course MIS 322 taught by Professor Staff during the Fall '08 term at Washington State University .

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final exam study guide 2 - Chapter 7 Conceptual data...

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