Week 5 - 18F - Lecture 5 - slides - I8F CLASS LECTURE - Copy - Copy.pdf

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DATABASE SYSTEMSCST 2355October, 2018Prof. Sandra Iroakazi
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Data Modeling with the Entity-Relationship Model
Lesson ObjectivesTo understand the purpose of the data modeling processTo understand entity-relationship (E-R) diagramsTo be able to determine entities, attributes, and relationshipsTo be able to create entity identifiers determine minimum and maximum cardinalitiesTo understand variations of the E-R model, entity types and be able to use ID-dependent and other weak entitiesTo understand and use entity patterns, ID-dependent association and multivalued attribute patterns.
The Data ModelA data modelis a plan or blueprint for a database design.A data model is more generalized and abstract than a database design.It is easier to change a data model than it is to change a database design, so it is the appropriate place to work through conceptual database problems.
Data Modeling in the SDLCThe Systems development life cycle (SDLC)as discussed in Appendix BData modeling occurs in the Requirements Analysisstep of the SDLCThe final data modelis part of the approved user requirements
Data Model = Conceptual DesignBooks on systems analysis and design often identify three design stages:Conceptual design (conceptual schema)Logical design (logical schema)Physical design (physical schema)The data modelwe are discussing is equivalent to the conceptual design as defined in these books.
Entity-Relationship (E-R) ModelThe Entity-Relationship (E-R) modelis a set of concepts and graphical symbols that can be used to create conceptual schemas.Versions:Original E-R modelby Peter Chen(1976)Extended E-R modelextensions to the Chen modelInformation Engineering (IE)by James Martin (1990); uses “crow’s foot” notation, is easier to understand, and we will use itIDEF1Xa national standard developed by the National Institute of Standards and Technology [see Appendix C]Unified Modeling Language (UML)by the Object Management Group; it supports object-oriented methodology
EntitiesSomething that can be identified and the users want to track:Entity classa collection of entities of a given typeEntity instancethe occurrence of a particular entityThere are usually many instances of an entity in an entity class.
CUSTOMER:The Entity Class and Two Entity Instances
AttributesAttributesdescribe an entity’s characteristics.

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