bogdan shishedjiev conceptual data model 1 conceptual data model principles graphical languages...
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Bogdan Shishedjiev Conceptual Data Model
1
Conceptual Data Model
PrinciplesGraphical Languages
ModelingConstraints
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Principles
• Main approach – object-oriented– Class (entity set, object)
– Association (relationship, relation)
– Data member (attribute, property)
– Instance (entity, occurrence)
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Languages
• Entity Relationship model (E-R) (ERM)– Entity set
– Relationship
– Attribute
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Languages
• MERISE– Object with occurrences
– Relation
– Propertiy
ENROLL
-NameSUBJECT
IS GIVENTEXTBOOK
-Name-Address
STUDENT
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Languages
• Object Role Modeling (ORM)
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Languages
• Class Diagram– Class with instances
– Association
– Property
+Name+FamilyName+Address
STUDENT
+SubName
SUBJECT+enrolls
*
+is enrolled
*
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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
Rules1. Every class has a one and only
one room. 2. Every subject is teaches by only
one teacher.3. Every class is taught a subject a
fixed number of hours.4. Every student can have no more
one mark in every subject.5. The school manages the
timetable and the rating of students and teachers..
Dictionary• Student’s Address,• Subject,• Number of Hours,• Class Name,• Student's Family Name,• Teacher‘s Name,• Mark,• Room Number,• Student’s Name
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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)
1.Attribute2.Attribute
NAME
1.First Name2.Last Name3.Address
STUDENT
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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
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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
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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
-TeacherName
TEACHER
-RoomNo
ROOM
-SubName
SUBJECT-End4
*-End3
*
-End5*
-HourNumber
Make cours
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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:– Unique Number– Name– address– Phone Number
2. General practitioner is characterized by:– Serial Number– Name– Phone Number
3. Each patient is supervised by a GP4. A policlinic is characterized by:
– Name– Address– Phone Number
5. A specialist is characterized by:– Serial Number– Name– Phone Number
6. Each specialist has one or more specialties
7. Each specialist can give consultations in one or more policlinics
8. Each policlinic groups several specialists
9. A patient can make an appointment for a consultation with specialist in a given policlinic, The specialist must work in this policlinic
10. The appointment is for a date that is later than the date of appointment
11. If the consultation does not take place a new appointment must be made no matter what are reasons for the failure
12. Lists of appointment for every specialist are made at the beginning of the day.
13. In the end of every day two reports are made:
– 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