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February 23 , 2002 Dr. A. K. Ramani 11
DESIGN METHODS
In previous section– General steps in DB development process , ISA ,EDM
– Database Architectures
AimDesign of conceptual Data Model
Objectives
• Understand – Conceptual Data Modeling
– Concepts of E-R Modeling
– Model Example & Limitations
RECAPRECAP
February 23 , 2002 Dr. A. K. Ramani 22
DESIGN METHODS
Purpose:– create detailed specification of internal documents and tasks from
the EDMInput:
– EDM, usage statistics, and other information gathered during the analysis
Output:– ER-Diagram, Data Representation, Constraints, Task
DecompositionsTechniques:
– data modeling – top-down decomposition of tasks until their specification is
sufficiently detailed to allow a programmer to implement them– task decomposition may result in tasks replacing the original task or
in subtasks controlled by the original taskTools: ER-Model
APPROACHAPPROACH
February 23 , 2002 Dr. A. K. Ramani 33
DESIGN METHODS
To build a
What is 1st Step ?What are the choices,Why ?• User Requirements
- User is not sure - Precise specification is difficult
• Communication Problems- Analyst & user communication- User not willing to take responsibility
Technical - Skills of modeler - Design Methodology – Non
Standard
CONCEPTUAL MODELCONCEPTUAL MODEL
February 23 , 2002 Dr. A. K. Ramani 44
DESIGN METHODS
Feasibility study
Requirement Analysis & Specifications
Data Modeling Process Modeling
Implementation Prototyping Testing
DESIGN APPROACHDESIGN APPROACH
February 23 , 2002 Dr. A. K. Ramani 55
DESIGN METHODS
Requirements Collection & Analysis
Conceptual Design (G)
Logical Design (Blue Print)
Physical Design
Application Design
Methods Req. Collection
Conceptual Model
Data Base System
DBMS
Tools , OS
Requirements Specs
Conceptual Database Model
Logical Models Performance Tests
Final Schema
Application PGMS
DESIGN PHASESDESIGN PHASES
February 23 , 2002 Dr. A. K. Ramani 66
DESIGN METHODS
Conceptual Design
Logical Design
Physical Design
Application Design
Requirement Collection & Analysis
C,Windows,Power Builder
ORACLE
Relational DBs
ER & ERR Model
Questionnaire & Interview
DESIGN METHODSDESIGN METHODS
February 23 , 2002 Dr. A. K. Ramani 77
DESIGN METHODS
• Models can be useful when we want to examine or manage part of the real world
• The costs of using a model are often considerably lower than the costs of using or experimenting with the real world itself
• Examples:– airplane simulator– nuclear power plant simulator– flood warning system– model of US economy– model of a heat reservoir– map
WHY TO USE MODELWHY TO USE MODEL
February 23 , 2002 Dr. A. K. Ramani 88
DESIGN METHODS
A Map Is a Model of Reality
MODEL OF REALITYMODEL OF REALITY
February 23 , 2002 Dr. A. K. Ramani 99
DESIGN METHODS
• A model is a means of communication• Users of a model must have a certain amount of
knowledge in common• A model on emphasized selected aspects• A model is described in some language• A model can be erroneous• A message to map makers: “Highways are not
painted red, rivers don’t have county lines running down the middle, and you can’t see contour lines on a mountain” [Kent 78]
MODEL TO RAISE QUESTIONMODEL TO RAISE QUESTION
February 23 , 2002 Dr. A. K. Ramani 1010
DESIGN METHODS
– A process that construct an abstract model which represents the entities,relationships and activities of an enterprise of real world
– Putting a Real World Object on to Paper
Purpose of model is to sharpen the question
MYCOM.COM
US $ 10 b
MCA/MMS
IIPS
CONCEPTUAL MODELINGCONCEPTUAL MODELING
February 23 , 2002 Dr. A. K. Ramani 1111
DESIGN METHODS
Why Conceptual Modeling ?• Obtain better understanding of business• Enable the end-user communication• Discover design errors at early stage• Build a Solid Foundation• Ensure the quality• A DBMS independent DB designWhat to Model ?• Static information
– Data - Entities– Associations - Relationship among entities
• Dynamic Information– Process – operations/transactions– Integrity constraints – Business Rules / Regulations
CONCEPTUAL MODELINGCONCEPTUAL MODELING
February 23 , 2002 Dr. A. K. Ramani 1212
DESIGN METHODS
• Process - Oriented Approach– Focus on activities, process & operations
Data Flow Diagram
• Data – Oriented Approach– Focus on data & their relationship– Characteristics of Data captured– Data more complex than process– Rich data source is the GOAL– Data is more stable than process– Data Orientation - Longer life
• Object – Oriented ApproachCombine data and process
CONCEPTUAL MODELING APPROACHESCONCEPTUAL MODELING APPROACHES
February 23 , 2002 Dr. A. K. Ramani 1313
DESIGN METHODS
• Entity – relationship model (ER) introduced in 1976 by Peter Chen
• Extended ER model (EER) expanded the original ER with new concepts
Lecturer Course
SSN
NameTeach
ER MODELINGER MODELING
Entity• An Entity is a conceptual object
• Physically or conceptually exists
• Usually a noun in requirement specification
E.g. Lecturer , Course , Movie , Sales-order
February 23 , 2002 Dr. A. K. Ramani 1414
DESIGN METHODS
• Collection of Entities have same properties• An entity instance is a single occurrence of entity
type• Described once in metadata• A noun in requirement specifications• A true data entity have many instances,each with
distinguishing feature• A strong entity – exists independently like student ,
Course , Car• A weak entity – existence depends upon other entity
(identifying owner)• Dependent
ENTITY TYPESENTITY TYPES
February 23 , 2002 Dr. A. K. Ramani 1515
DESIGN METHODS
• Property , description of entities and entity types• Attribute type ( domain)
– Define all possible attribute values
• Attribute value , associated with individual entities• A noun or an objective in requirement specifications
IM-99-02Student
ID
DoB
Singh
4-9-77
Entities – Attributes
•Entities have ‘independent’ meaning e.g. Car , Student
•Attributes have no independent meaning ? ID
ATTRIBUTEATTRIBUTE
February 23 , 2002 Dr. A. K. Ramani 1616
DESIGN METHODS
• Uniquely identify individual instances of an entity
type– A key refers to one or a group of attributes as a whole– A key attribute refers to a component of a composite
key– Definition of a key changes with Data Semantics
• An entity type may have few keys – Primary key – One of candidate key– Secondary key – Other keys
• The primary key attribute (s) underlined• Choose key – will not change• Choose key – Not Null• Avoid INTELLIGENT KEYS
KEY ATTRIBUTEKEY ATTRIBUTE
February 23 , 2002 Dr. A. K. Ramani 1717
DESIGN METHODS
• Simple attribute– Can’t be broken into smaller values– Contains only atomic values
• Composite attribute– Has component attribute
• Single valued attribute– One only per attribute
• Multi – Valued attribute– Contains multiple values
ATTRIBUTE CLASSIFICATIONATTRIBUTE CLASSIFICATION
February 23 , 2002 Dr. A. K. Ramani 1818
DESIGN METHODS
Student
Roll No
Skill
Dob
F.Name
M.Name
L.Name
Name
Degree
EXAMPLEEXAMPLE
February 23 , 2002 Dr. A. K. Ramani 1919
DESIGN METHODS
• It is an association among instances of one or more
entities involved.– Label as– Verb in requirement specifications,in present tense &
descriptive– Example
– Model associations, not actions and process
Student Course
Faculty
Teach
take
advise
RELATIONSHIPRELATIONSHIP
February 23 , 2002 Dr. A. K. Ramani 2020
DESIGN METHODS
• How is an entity linked to relationship ? [Participation]
• How many relationship instances is an entity permitted to be linked to ? [cardinality]
• Relationship instance is an association between entity instances, where each instance includes exactly one entity from each participating entity type
Student Advise Faculty
Akr
Trupti
Kris
Ram
Mohan
Singh
JUSTIFICATIONJUSTIFICATION
February 23 , 2002 Dr. A. K. Ramani 2121
DESIGN METHODS
E1E2R
min,max min,max
Participation
0 – Partial
1 - Total
Cardinality
1 - - One
M - - More than One
O - - One
Advise Faculty
X
Z
Y
A
B
CD
Student
CARDINALITY AND PARTICIPATIONCARDINALITY AND PARTICIPATION
February 23 , 2002 Dr. A. K. Ramani 2222
DESIGN METHODS
Unary Relationship
Binary Relationship
Ternary/N-ary Relationship
RELATIONSHIP DEGREESRELATIONSHIP DEGREES
February 23 , 2002 Dr. A. K. Ramani 2323
DESIGN METHODS
Person Married
(0,1)
(0,1)
Employee Manager
(0,m)
(0,1)
Unary RelationshipRELATIONSHIP DEGREERELATIONSHIP DEGREE
February 23 , 2002 Dr. A. K. Ramani 2424
DESIGN METHODS
One –to-one binary RelationshipA BCD
X
Y
Z
A
One –to-Many binary Relationship
BCD
X
Y Z
E1 E2(1, 1) (0, m)
BINARY RELATIONSHIPBINARY RELATIONSHIP
February 23 , 2002 Dr. A. K. Ramani 2525
DESIGN METHODS
Many to Many binary Relationship
E1 E2R1(0, m) (1, m)
X
Y
Z
A
B
C
D
BINARY RELATIONSHIPBINARY RELATIONSHIP
Justification
February 23 , 2002 Dr. A. K. Ramani 2626
DESIGN METHODSCustomer
SELL
SalesmanCar
TERNARY RELATIONSHIPTERNARY RELATIONSHIP
CAR REP(0,1) (0, m)
Sell
Customer
(0,M)
February 23 , 2002 Dr. A. K. Ramani 2727
DESIGN METHODS
Unary
n-aryto
RELATIONSHIP DEGREERELATIONSHIP DEGREE
February 23 , 2002 Dr. A. K. Ramani 2828
DESIGN METHODS
Relationship attributes• Attributes describing relationship, like when ,where, what
FacultyStudent Advise
MemoTime
Date
• A relationship instance must include all participants
• Need to be careful when converted to binary relationship
RELATIONSHIP ATTRIBUTESRELATIONSHIP ATTRIBUTES
February 23 , 2002 Dr. A. K. Ramani 2929
DESIGN METHODS
Attributes on a relationship might suggest to convert it to entity , termed (---) as associative entity.
CourseEMP Completes
Date
m m
CERT
Date Number
ASSOCIATIVE ENTITYASSOCIATIVE ENTITY
February 23 , 2002 Dr. A. K. Ramani 3030
DESIGN METHODS
• Conditions– Result entity independent meaning
– Result entity participates in one or more other relationships
Other Notations
Mandatory One
Mandatory Many
Optional One
Optional Many
CONDITIONS AND NOTATIONSCONDITIONS AND NOTATIONS
February 23 , 2002 Dr. A. K. Ramani 3131
DESIGN METHODS
BASIC E-R NOTATIONBASIC E-R NOTATION
February 23 , 2002 Dr. A. K. Ramani 3232
DESIGN METHODS
SAMPLE ER DIAGRAMSAMPLE ER DIAGRAM
February 23 , 2002 Dr. A. K. Ramani 3333
DESIGN METHODS
• Conceptual Modeling – important skill• Conceptual Schema important design
document – independent of DBMS• Entities , types• Relationships Unary – n-ary• Associations
– Cardinality (Connectivity)– Participation (Degree)
SUMMARYSUMMARY