Entity-Relationship Diagrams
Contents: Data Modeling User Views Entities/ Entity Sets Attributes Entity-Relationship Diagrams (ERDs) Finding Entities and Relationships English Grammar Rules Registration Example Student Registration Course Enrollment Grade Report Relationship Attributes Extended ERD Note: The Entity-Relationship Diagrams presented in this class are based on James Martin’s Information Enginnering approach.
Georgia State University--CIS 850/330 Entity Relationship Modeling
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Design Approach
User View Collection of Tables
2. Normalize these relations Steps: 1. Model User View
Collection of BCNF Tables
3. Represent all keys
Collection of BCNF Tables with Keys Represented New Cumulative Design Old Cumulative Design
Georgia State University--CIS 850/330 Entity Relationship Modeling
4. Merge the result of the previous steps into the cumulative design.
Model User View
Advantages of Data Modeling:
+ Data Analysis vs. Process Analysis + Graphical Models vs. Prose + “Data is more stable than processes.”
Georgia State University--CIS 850/330
Entity Relationship Modeling
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User Views
A user view is the view of the data that is necessary to support the operations of a particular user. Example: Wells Junior College User View #1 -- Registration User View #2 -- Class Enrollment User View #2 -- Grade Reporting
Georgia State University--CIS 850/330
Entity Relationship Modeling
Entities/ Entity Set
An entity is a person, place, object, event, or concept about which the organization wishes to record data. Rules: An entity . . . 1. Must be within the scope of the system 2. Must have at least one non-key attribute An entity type is a collection of entities with a similar data structure.
