Lecture 4 -...

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Week 4: Data Modeling and Design Strategy - Lecture Help Print This Page Data Modeling Conceptual Data Modeling | Entity-Relationship Modeling | Creating Alternative Design Solutions | Selecting the Most Likely Alternative | Updated Baseline Project Plan Conceptual Data Modeling An abstract data model is a very comprehensive description of the system showing the overall data structure within the organization. An entity-relationship diagram (E-R) is often used to show the data organization within the system. Systems analysts use surveys, user interviews, questionnaires, or JAD sessions to collect information for the modeling. The systems analyst creates conceptual models for the existing system, and another for the new system. The development life cycle requires many data models to be created. The logical model of the data is prepared during the third phase - the design phase . A design of the database also takes place, but the actual data definitions and the expanded data model are not prepared until the fourth phase (implementation and operation). A project repository associates the database design and the data models. The primary deliverable of conceptual modeling is the entity-relationship diagram. Up to four E-R diagrams may be created for conceptual modeling: A diagram for the data needed for applications. 1. A diagram for the existing system. 2. A diagram for the new database for the new system. 3. A diagram for the old database from the current system. 4. Entity-Relationship Modeling E-R diagrams contain three pieces of information: Entities . An entity is an object representing something in the real world, such as a person, thing, place, or an event that the business needs to track. An entity type is a grouping of like entities sharing common attributes, and an instance is a single entity. 1. For example, courses would be an entity type; there are science courses, math courses, and business courses, etc. So the type is a way to group entities. Instances of an entity from a business course would be MGMT340, a specific course. In a diagram, entities are drawn using a rectangle. Attributes
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This note was uploaded on 12/28/2010 for the course MGMT 340 taught by Professor Kerns during the Spring '10 term at DeVry Columbus North.

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Lecture 4 -...

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