System analysis and design
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Transcript of System analysis and design
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SYSTEM ANALYS
IS AND
DESIGN
S A F A A S. Y
. DA L L O U L
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DATA MODELING
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UNIT 7: DATA MODELINGData 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
Creating an ERD Steps in Building ERDs Add attributes and assign
identifiers Identify relationships
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KEY DEFINITIONS
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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.
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CONCEPTUAL DATA MODEL
Describes WHAT the system
contains
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LOGICAL DATA MODEL
Shows the organization of data without indicating how it is
stored, created, or manipulated.
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PHYSICAL DATA MODEL
Shows how the data will actually be stored in databases or
files.
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NORMALIZATION
It is the process analysts use to validate data
models
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ENTITY RELATIONSHIP DIAGRAM
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WHAT IS AN ERD
UniversityStudent
PK StudentID
StudentName StudentDOB StudentAge
Entity
Attributes
Primary key
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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
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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
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EXAMPLE OF ERD
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READING ERD
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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 …
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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
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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
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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.
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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
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WHAT IS AN ERD ELEMENTS
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CREATING AN ERD
Drawing the ERD is an iterative process of trial and
revision
ERDs can become quite complex
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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
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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
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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
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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
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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.
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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
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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.
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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)
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FIRST NORMAL FORM (1NF)
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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.
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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).
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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.
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SECOND NORMAL FORM (2NF)
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SECOND NORMAL FORM (2NF)
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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.
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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.
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THIRD NORMAL FORM (3NF)
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THIRD NORMAL FORM (3NF)
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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.
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EXERCISES
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.
Draw an entity relationship diagram for the following situations:
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EXERCISES
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.
Draw an entity relationship diagram for the following situations:
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SAFAA S.Y. DALLO
UL
S A F A A D A L L O U L . WO R D P R E S S . C
O M
Thank
You