Enhanced entity-relationship modelling concepts. (Lecture 3) презентация

Содержание

Enhanced Entity-Relationship Modelling Concepts Lecture 3

Слайд 2Enhanced Entity-Relationship Modelling Concepts
Lecture 3


Слайд 3Agenda
1.Relationships with degree higher then 2

2.EER concepts specialisation/generalisation

3.Alternative ER/EER notation


Слайд 41.Relationships with degree higher then 2
Cardinality
Participation
Entity
Type
Occurrence
Strong
Weak
Multiplicity
Relationship
Type
Occurrence
Degree
Attribute
Complex
Simple
Single valued
Multi valued


Слайд 51.Relationships with degree higher then 2
Degree of a Relationship
Number of participating

entities in relationship.

Relationship of degree:
two is binary;
three is ternary;
four is quaternary.


Слайд 61.Relationships with degree higher then 2
Ternary relationship called ‘Registers’


Слайд 71.Relationships with degree higher then 2
Quaternary relationship called ‘Arranges’


Слайд 81.Relationships with degree higher then 2
Multiplicity for Complex Relationships
Number (or

range) of possible occurrences of an entity type in an n-ary relationship when other (n-1) values are fixed.

Слайд 91.Relationships with degree higher then 2
Ternary relationship called ‘Registers’


Слайд 101.Relationships with degree higher then 2
Ternary relationship called ‘Registers’ with Values

for Staff and Branch Entities Fixed


Слайд 111.Relationships with degree higher then 2
Try to detect multiplicities for remaining

participating entities in ternary relationship Registers
Note: You can make appropriate assumptions and detect multiplicities accordingly


Слайд 12Agenda
1.Relationships with degree higher then 2

2.EER concepts specialisation/generalisation

3.Alternative ER/EER notation


Слайд 132.1.The Enhanced Entity-Relationship Model
Semantic concepts are incorporated into the original ER

model and called the Enhanced Entity-Relationship (EER) model.
Examples of additional concepts of EER model are:
specialization / generalization;
aggregation;
composition.


Слайд 142.2. Specialisation/Generalisation
Superclass
An entity type that includes one or more distinct subgroupings

of its occurrences.

Subclass
A distinct subgrouping of occurrences of an entity type.


Слайд 152.2. Specialisation/Generalisation
Superclass/subclass relationship is one-to-one (1:1).

Superclass may contain overlapping or

distinct subclasses.

Not all members of a superclass need to be a member of a subclass.


Слайд 162.2. Specialisation/Generalisation
Attribute Inheritance
An entity in a subclass represents same ‘real world’

object as in superclass, and may possess subclass-specific attributes, as well as those associated with the superclass.


Слайд 172.2. Specialisation/Generalisation
Specialization
Process of maximizing differences between members of an entity

by identifying their distinguishing characteristics.

Generalization
Process of minimizing differences between entities by identifying their common characteristics.


Слайд 182.2. Specialisation/Generalisation


Слайд 192.2. Specialisation/Generalisation


Слайд 202.2. Specialisation/Generalisation


Слайд 212.2. Specialisation/Generalisation


Слайд 222.3. Multiplicity constraints in Specialisation/Generalisation
Participation constraint
Determines whether every member in superclass

must participate as a member of a subclass.
May be mandatory (total) or optional.


Слайд 232.3. Multiplicity constraints in Specialisation/Generalisation
Disjoint constraint
Describes relationship between members of

the subclasses and indicates whether member of a superclass can be a member of one, or more than one, subclass.
May be disjoint (OR) or overlapping (AND)


Слайд 242.3. Multiplicity constraints in Specialisation/Generalisation


Слайд 252.3. Multiplicity constraints in Specialisation/Generalisation


Слайд 262.3. Multiplicity constraints in Specialisation/Generalisation


Слайд 272.4. EER


Слайд 282.5. Aggregation
Represents a ‘has-a’ or ‘is-part-of’ relationship between entity types, where

one represents the ‘whole’ and the other ‘the part’.



Слайд 292.6. Composition
Specific form of aggregation that represents an association between entities,

where there is a strong ownership and coincidental lifetime between the ‘whole’ and the ‘part’.



Слайд 30Agenda
1.Relationships with degree higher then 2

2.EER concepts specialisation/generalisation

3.Alternative ER/EER notation


Слайд 313.1. Chen’s ER-diagram notation

Meaning
ENTITY TYPE
WEAK ENTITY TYPE
RELATIONSHIP TYPE
IDENTIFYING RELATIONSHIP TYPE
ATTRIBUTE
KEY ATTRIBUTE
MULTIVALUED

ATTRIBUTE
COMPOSITE ATTRIBUTE
DERIVED ATTRIBUTE
TOTAL PARTICIPATION OF E2 IN R
CARDINALITY RATIO 1:N FOR E1:E2 IN R
STRUCTURAL CONSTRAINT (min, max) ON PARTICIPATION OF E IN R

Symbol



R

E2

E1


R

E2


R

(min,max)

E

N



Слайд 323.1. Chen’s ER-diagram notation


Слайд 333.1. Chen’s ER-diagram notation


Слайд 343.1. Chen’s ER-diagram notation


Слайд 353.1. Chen’s ER-diagram notation


Слайд 363.1. Chen’s ER-diagram notation


Слайд 373.1. Chen’s ER-diagram notation


Слайд 38Reading
Connolly & Begg, Chapter 13


Обратная связь

Если не удалось найти и скачать презентацию, Вы можете заказать его на нашем сайте. Мы постараемся найти нужный Вам материал и отправим по электронной почте. Не стесняйтесь обращаться к нам, если у вас возникли вопросы или пожелания:

Email: Нажмите что бы посмотреть 

Что такое ThePresentation.ru?

Это сайт презентаций, докладов, проектов, шаблонов в формате PowerPoint. Мы помогаем школьникам, студентам, учителям, преподавателям хранить и обмениваться учебными материалами с другими пользователями.


Для правообладателей

Яндекс.Метрика