lect6 - 1.264 Lecture 6 Data modeling 1 Data models Data...

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1.264 Lecture 6 Data modeling
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1. Data models Data model is representation of Things (or entities or objects) of importance to a business How the things relate to each other It is built and modified until it represents the business well enough to write a system. Data models are extended to become class diagrams in the Unified Modeling Language [UML] by adding the behaviors of each entity to the model Data models are sometimes built during requirements, and other times during design phase The earlier the better. I always build them during requirements.
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Logical data modeling Method to discover the data, relationships and rules of a business, collectively called the business rules Logical data models are the basis of: Physical data models, or actual databases Applications, parts of which can be automatically generated from the data model Small model for broker of transportation services Small, but says a lot about broker Gives good picture of what database should look like Also gives good picture of underlying business rules of broker Useful in requirements analysis and scrubbing!
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Transportation Broker Data Model
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Broker Business Rules A carrier can be associated with many offices An office can be associated with many carriers A carrier can issue many contracts A contract is issued by one carrier An office can employ many agents An agent is employed by one office An agent can sell many contracts A contract is serviced by only one agent A contract can serve to carry only one commodity type A commodity type can be carried under many contracts A contract can be associated with many equipment types An equipment type can be associated with many contracts A customer can be served by many contracts A contract covers one customer
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Data model purpose Business needs to build logical data model so users and developers both understand business rules of company Models enable users and developers to have single view of system Sometimes users note this is first time they understood business rules! Converting logical to physical data model (database) is very straightforward these days. Little need for separate physical model for online databases Create integer system-generated keys instead of strings and composite keys for performance We still create separate physical models for data warehouses, read-only databases and some other special cases
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2. Data modeling concepts Entities (objects, tables) Attributes (properties) Keys (primary and foreign) Relationships Referential integrity
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lect6 - 1.264 Lecture 6 Data modeling 1 Data models Data...

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