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System analysis and design. Safaa s.y. dalloul. Data Modeling. Unit 7: Data Modeling. Creating an ERD Steps in Building ERDs Add attributes and assign identifiers Identify relationships. Data Modeling Key Definition Data Model Logical Data Model Physical Data Model Normalization

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system analysis and design

System analysis and design

Safaa s.y. dalloul

unit 7 data modeling
Unit 7: Data Modeling
  • Creating an ERD
    • Steps in Building ERDs
    • Add attributes and assign identifiers
    • Identify relationships
  • Data Modeling
    • Key Definition
      • Data Model
      • Logical Data Model
      • Physical Data Model
      • Normalization
    • Entity Relationship Diagram
      • What Is an ERD?
      • Using the ERD to Show Business Rules
      • Reading ERD
      • Elements of ERD
slide5

Data Model

  • A formal way of representing the data that are used and created by a business system.
  • Shows the people, places and things about which data is captured and the relationships among them.
slide6

Conceptual Data Model

Describes WHAT the system contains

slide7

Logical Data Model

Shows the organization of data without indicating how it is stored, created, or manipulated.

slide8

Physical Data Model

Shows how the data will actually be stored in databases or files.

slide9

Normalization

It is the process analysts use to validate data models

slide11

What is an ERD

Entity

Primary key

Attributes

slide12

What is an ERD

  • A picture/drawings showing the information created, stored, and used by a business system.
  • Entities generally represent similar kinds of information
  • Lines drawn between entities show relationships among the data
  • High level business rules are also shown
slide13

Using the ERD to Show Business Rules

  • Business rules are constraints that are followed when the system is in operation.
  • ERD symbols can show when one instance of an entity must exist for an instance of another to exist.
  • A doctor must exist before appointments for the doctor can be made
slide16

Reading ERD

  • This diagram implement the ERD for a doctor Office system
  • Data can be organized into six different categories (Patients, Appointment, doctors, bill, Payments, and Insurance company)
  • The Patient information include patient’s ID number, last name, first name, address phone number …
slide17

Reading ERD

  • Each category has a piece of information used to uniquely identify it, as examples:
  • Patient ID number uniquely identify each patient
  • Bill number uniquely identify each bill
slide18

Reading ERD

  • The lines connecting the six categories communicate the relationships that categories share. So you can understand that a doctor is scheduled by an appointment that is scheduled by a patient
slide19

Reading ERD

  • ERD is also presents high level business rules. Business rules are constraints or guidelines that are followed during the operation of the system.. They are rules like
  • Only one person can be seen by a doctor at a time
  • Payments can be made in the form of cash or check
  • Payment can be paid by insurance, patient, or combination of both.
slide20

Reading ERD

  • On the data model business rule are communicated by relationships, in example
  • A patient can schedule by many appointment
  • A person does not have to be insured to become a patient
slide22

Creating an ERD

  • Drawing the ERD is an iterative process of trial and revision
  • ERDs can become quite complex
slide23

Steps in Building ERD

  • Identify the entities
    • Identify major categories of information
    • Verify that there is more than one instance of the entity that occurs in the system
slide24

Steps in Building ERD

  • Add attributes and assign identifiers
    • Identify attributes of the entity that are relevant to the system under development
    • Select the entity’s identifier
slide25

Steps in Building ERD

  • Identify Relationships
    • Start with an entity and identify all entities with which it shares relationships
    • Describe the relationship with the appropriate verb phrase
    • Determine the cardinality and modality by discussing the business rules with knowledgeable users
slide26

Advanced Syntax

  • Independent Entity
    • Is an entity that can exist without the help of another entity, such as doctor, patient, and insurance company
    • These entities all have identifiers that were created using there own attributes
slide27

Advanced Syntax

  • Dependent Entity
    • In some situations the child entity does required attributes from the parent entity to uniquely identify an instance.
    • This child entity called dependent entity, such as the appointment entity, which uses the physicianidnumber from doctors entity.
slide28

Advanced Syntax

  • Intersection Entity
    • It exists in order to capture some information about the relationship that exists between two other entities.
    • Typically intersection entity are added to logical data model to store information about two entities sharing an many to many relationship
slide29

Normalization

  • It is a technique helps analysts to validate the model that they have drawn.
  • It is a process whereby a series of rules are applied to a logical data model to determine how well it formed is.
slide30

First Normal Form (1NF)

  • A logical data model in first normal form (1FN) if it not contains attributes that have repeating values for a single instance of an entity.
  • This form should solve repeating attributes and repeating groups’ problems.
  • Note the following example of the entity (special orders)
slide32

First Normal Form (1NF)

  • The attribute customer book preferences are a list of kind of books customers like to read.
  • As you note there are a repeating attribute which is the preferences
  • And there is another repeating group with Books. This group of (isbn, name, author,publicationyear, authoruniversity) they all may repeated many times for each special orders.
slide33

Second Normal Form (2NF)

  • In this form, for each entity, the attributes that serve as identifier can determine the value for all of the other attributes for an instance in an entity.
  • In the last example, the special order entity had three attributes that were used as identifiers (special order date, customer last name, and customer first name).
slide34

Second Normal Form (2NF)

  • These attributes used to identify a customer, but can not identify the special form attributes such as order status.
  • To resolve the problem, anew entity called Customer was created.
slide37

Third normal Form (3NF)

  • Occurs when a model is in both 1NF and 2NF and when in the resulting entities none of the attributes are dependent on a non identifier attribute.
  • In our example this problem with the book entity is that the author university is dependent on the author.
slide38

Second Normal Form (2NF)

  • And in the special order entity Store name, location and manager are not dependent on special order.
  • To resolve this problem an entity called author was created, and another entity called store was created.
slide41

Third normal Form (3NF)

  • Third normal form is also address problem caused by derived, or calculated, attributes. No need to store calculated attributes such as the age if we already stored the birthrate.
  • In our example, we dropped the attribute days in order from special order entity because it can be derived from special order date.
slide42

Exercises

  • Draw an entity relationship diagram for the following situations:

Whenever new patients are seen for the first time, they complete a patient information form that asks their name, address, phone number, and insurance carries, all of which is stored in the patient information file. Patient can be signed up with only with only carrier, but they must be signed up to be seen by the doctor. Each time a patient visits the doctor, an insurance claim is sent to the carrier for payment. The claim must contain information about the visit. Such as date, purpose, and cost. It would be possible for a patient to submit to claims on the same day.

slide43

Exercises

  • Draw an entity relationship diagram for the following situations:

A department store has a bridal registry. This registry keeps information about the customer (usually the bride), the products that the store carries, and the products for which each customer registers. Customer typically registers for the same products.

safaa s y dalloul
Safaa S.y. dalloul

Safaadalloul.wordpress.com

Thank You