DM Building Blocks

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Data Models

By

Rajesh Kumar

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Data Model Basic Building

Blocks EntityAnything about which data will be collected/stored

Attribute

Characteristic of an entity Relationship

escribes an association among entities !ne"to"one #1$1% relationship

!ne"to"many #1$&% relationship

&any"to"many #&$' or &$&% relationship

ConstraintA restriction placed on the data

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Business Rules

Brief) precise and unambiguous descriptions of

policies) procedures or principles within the

organi*ation

escribe characteristics of the data as +iewed by the

company

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,

Translating Business Rulesto Data Model Components -tandardi*e company.s +iew of data

Communication tool between users and designersAllow designer to understand the nature) role and scope

of dataAllow designer to understand business processes

Allow designer to de+elop appropriate relationshipparticipation rules and constraints

romote creation of an accurate data model 'ouns translate into entities

0erbs translate into relationships among entities Relationships are bi"directional

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The Relational Model

Conceptually simple 3in4ed 5ables

e+eloped by Edgar 67 Codd #8B& 19:; % Considered ingenious but impractical in 19:;

Computers lac4ed power to implement the relational model

5oday.s Cs run sophisticated relational databases

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ow data are physically stored is of no concern to

the user or the designer 5he source of a real database re+olution

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Relational Model Relational

Diagram

Representation of

relational database.s

Entities #5ables%

Attributes within those

entities #6ields% Relationships between

those entities #3in4s%

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The Relational Model SQL

-tructured @uery 3anguage #-@3%

Allows ad hoc ueries uestions of the data

ser can specify what must be done without

specifying how it must be done ominance due in great part to its powerful and

fle=ible uery language

-@3"based relational database application$

ser interface

A set of tables stored in the database

-@3 engine

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Entity Relationship Model ERM!

8ntroduced by eter Chen in 19: