# Conceptual Data Model (PowerPoint) by pptfiles

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```									Conceptual Data Model

Principles
Graphical Languages
Modeling
Constraints

Bogdan Shishedjiev Conceptual Data   1
Model
Principles
• Main approach – object-oriented
–   Class (entity set, object)
–   Association (relationship, relation)
–   Data member (attribute, property)
–   Instance (entity, occurrence)

Bogdan Shishedjiev Conceptual Data Model   2
Languages
• Entity Relationship model (E-R) (ERM)
– Entity set
– Relationship
– Attribute

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Languages
• MERISE
– Object with occurrences
– Relation
– Propertiy

ENROLL

STUDENT                                                        SUBJECT
-Name
-Name
TEXTBOOK

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Languages
• Object Role Modeling (ORM)

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Languages
• Class Diagram
– Class with instances
– Association
– Property

STUDENT
+enrolls     +is enrolled          SUBJECT
+Name
+FamilyName                                    +SubName

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Conceptual Model
• Goals
– Starting from the dictionary and the rules this model tries to reveal
the relations among the data and their interaction
• Example – School
Rules                                         Dictionary
1. Every class has a one and only             • Student’s Address,
one room.                                  • Subject,
2. Every subject is teaches by only           • Number of Hours,
one teacher.                               • Class Name,
3. Every class is taught a subject a          • Student's Family Name,
fixed number of hours.                     • Teacher‘s Name,
4. Every student can have no more             • Mark,
one mark in every subject.                 • Room Number,
5. The school manages the                     • Student’s Name
timetable and the rating of
students and teachers..

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Concepts
• Class (Entity class, Entity instance)
• Association
– Relationship between entity instances
• Attribute
– Properties

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Defining an Entity Class
• Give it a name (a noun)
• Define its attributes
• Define the rules
– What belongs to the class?
– How the instances are identified in the class?
• Identifying an instance (Identifier)

NAME                                       STUDENT
1.First Name
1.Attribute                                 2.Last Name

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Association
• Give a name (a verb)
• Determine the
participating classes
• Define the cardinalities

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Examples

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Identifier of an Association

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Cardinalities of an Association
•   Cardinalities One to One
–   0..1 – 0..1 – Every student
can use one locker

–   0..1 – 1

–   1 – 1 Every student uses
a locker and ther are no
free lockers

Bogdan Shishedjiev Conceptual Data Model   13
Cardinalities of an Association
• Cardinalities One to Many
– 1 – 1..N

– 0..1 – 1..N

– 1 – 0..N

– 0..1 – 0..N

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Cardinalities of an Association
• Cardinalities Many to
Many
– 1..N – 1..N

– 0..N – 1..N

– 0..N – 0..N

Bogdan Shishedjiev Conceptual Data Model   15
Cardinalities of an Association
•   Generalization
– Minimal cardinality
•    Mandatory participation of every instance - 1
•    Optionally participation of every instance - 0
– Maximal cardinality
•    To only one instance of the other class – 1
•    To multiple instances of the other class - N

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Dimension of an Association
• Number of different classes participating in it
• Multidimensional

Make cours
-HourNumber

-End4                        -End3
TEACHER         *                            *      SUBJECT
-TeacherName                                        -SubName
-End5
*

ROOM
-RoomNo

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Dimension of an Association
•   Multidimensional

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Dimension of an Association
•   One-dimensional
(Reflexive)

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Aggregate Associations
• Aggregation

• Composition

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Weak Entities
• It is identified through the association

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Recommendations
• Don’t use high dimension associations
• Be aware not replace classes by associations

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Case Study – Management Rules
1.   A patient is characterized by:             6. Each specialist has one or more
–   Unique Number                              specialties
–   Name                                   7. Each specialist can give consultations
–   address                                    in one or more policlinics
–   Phone Number                           8. Each policlinic groups several
2.   General practitioner is characterized          specialists
by:                                        9. A patient can make an appointment for
–   Serial Number                              a consultation with specialist in a given
–   Name                                       policlinic, The specialist must work in
–   Phone Number                               this policlinic
3.   Each patient is supervised by a GP         10. The appointment is for a date that is
4.   A policlinic is characterized by:              later than the date of appointment
–   Name                                   11. If the consultation does not take place a
–   Phone Number
matter what are reasons for the failure
5.   A specialist is characterized by:          12. lists of appointment for every specialist
are made at the beginning of the day.
–   Serial Number
–   Name                                   13. In the end of every day two reports are
–   Phone Number
–   A log of appointment made
–   A log of consultations done

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Case Study - Policlinic

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Case Study - Policlinic

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Subtypes
• Example – Hardware
components order

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Subtypes

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