Agenda & Objectives Agenda Overview where data

Transcript:Agenda & Objectives Agenda Overview where data:
Agenda & Objectives Agenda Overview where data modeling fits within SDLC Define data modeling components Write business rules Practice modeling various relationships Objective Given an existing entity relationship diagram (ERD), you will be able to create the corresponding business rules. Given an existing entity relationship diagram, you will be able to describe the business process. Resource BusRules_InterpretingERD.pptx STRUCTURING SYSTEM REQUIREMENTS: CONCEPTUAL DATA MODELING IS 310 Dr. Jean A. Pratt Text/visual support from Valacich, George, Hoffer (© 2006 Prentice-Hall, Inc. ); Dennis, Wixom, Roth (© 2006 John Wiley & Sons, Inc.); Dr. Bruce Lo Creating Business Rules; Interpreting ERDs Data Modeling Outline Overview of data modeling Deliverables of data modeling Questions to ask when gathering information Where data modeling maps to process modeling Elements of ERD Cardinality, participation Degree of relationships Identifying or non-identifying PK? Overview of Data Modeling A model that captures the overall structure of organizational data, independent of DBMS and without implementation details Deliverable Entity Relationship Diagram Gathering Information Questions for Data Modeling 1. What are subjects/objects of the business? * Entities 2. What unique characteristic distinguishes each object from other objects of the same type? * Primary key 3. What characteristics describe each object? * Attributes 4. How do you use this data? * Reports (via queries) * Security controls (e.g., login requirements) Questions (cont’d…) 5. How many instances of one entity participate with another entity? * Cardinality 6. Is participation between entities required or optional? * Participation 7. What events occur that imply associations between various objects? * Relationships 8. Is each activity or event always handled the same way or are there special circumstances? * Integrity rules and triggers Outline Overview of data modeling Elements of ERD Entity Attribute Identifier/Primary Key Relationships and Business Rules ERD Notations: Chen and Crow’s Foot Cardinality, participation Degree of relationships Identifying or non-identifying PK? Entity A person, place, object, event or concept in user environment about which the organization wishes to maintain data E.g., employee, student, warehouse, car, sale, booking, account, course Note the difference Entity Entity instance Attribute A property or characteristic of an entity of interest to the organization Many CASE tools do not include attributes on the ERD to avoid cluttering the diagram, but define them in the repository E.g., STUDENT (Stud_Id, Stud_name, Address, Phone) E.g., AUTOMOBILE (Vehicle_Id, Color, Horsepower, Year) Candidate Key An attribute (or combination of attributes) that uniquely identifies each entity instance Identifier/Primary