Lec-4 Overview of Database Design

7/29/2019 Lec-4 Overview of Database Design

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Database

Design InEntity-RelationshipModel

Unit II


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Process of producing a detailed data

model of a database

Contains all the needed logical and physicaldesign choices and physical storageparameters needed to generate a design ina Data Definition Language, which can thenbe used to create a database

The overall process of designing, not justthe base data structures, but also the formsand queries used as part of the overalldatabase application within the databasemanagement system (DBMS).

DATABASE DESIGN


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1) Requirement Analysis:

Data to be stored can be determined byRequirement Specification.

Application is to be built on top of database

Most frequent operations & performancerequirements

Discussions with user group & study ofcurrent operating environment

Skill on the part of the database designerto elicit the needed information fromthose with the domain knowledge

DATABASE DESIGNPROCESS


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2) Conceptual Databse Design:

Once a database designer is aware of the datawhich is to be stored within the database, theymust then determine where dependency iswithin the data.

Carried out using ER model.

ER model is one of the several high level datamodels used in database design.

The goal is to create a simple descriptionof data that closely matches with howusers & developers think of data.



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3) Logical Databse Design:

Once the relationships and dependencies amongst thevarious pieces of information have been determined, it is

possible to arrange the data into a logical structure whichcan then be mapped into the storage objects supported bythe database management system

Choose s DBMS

Convert ER schema into a relational database schema

Each table may represent an implementation of either alogical object

Relationships between tables may then be stored as linksconnecting child tables with parents.



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4) Schema Refinement:

To analyze the collection of relations

To identify potential problems and refine it

In contrast to requirements analysis and

conceptual design which are subjective,schema refinement is guided by someelegant theory.

E.g. theory on Normalizing



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5) Physical database design :

specifies the physical configuration ofthe database on the storage media

includes detailed specification of dataelements, data types, indexing optionsand other parameters residing in theDBMS data dictionary

It is the detailed design of a systemthat includes modules & the database'shardware & software specifications ofthe system.


S S G


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6)Application & Security design :

Define the role of each user, group anddepartments working on Database

Identify the parts of database that canbe accessed or can not be accessed.

Ensure access rules and authorizationprivileges to be enforced

Design methodologies like UML (unifiedModeling Language) try to addresscomplete software design anddevelopment cycle.



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ERD can be summarized as the process of uncovering,analyzing, and explicating (i.e., stating clearly and fully) thebusiness rulesgoverning a application.

ERD

Entities: An object in the real world that is distinguishablefrom other objects - Information holding structures

Attributes: Properties, characteristics, associated with anentity.

Domain : With each attribute , domain of possible values

Key: Minimal set of attributes whose values uniquely identifyan entity. If there are more then we identify one as primarykey.

Relationships: Connections between entities

Cardinalities: Upper bounds

Modalities: Lower bounds

a s n y- e a ons pDiagrams?


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E-R analysis relies heavilyon diagrams to represent

Entities (rectangles)

Attributes (ellipses)

Relationships (diamonds) Connections (lines, which may

have arrowheads to representdegrees of connectivity orrelationship)

E-R Diagrams (1)

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Lec-4 Overview of Database Design