DATABASE:
Is
an organized collection of related information, which you probably encounter
severally everyday. For instance you take care of your personal business with
databases such as your cheque book, address book and phone book or diary.
DATABASE MANAGEMENT SYSTEM:
Is
set of tools to help you manage a database. For instance assuming you are
running a typical business of buying and selling and you add new stock cards
for new items of stock or you try to check the stock balance in your organization.
We have data modeling and date
models
DATA MODELING:
It
can be the process of creating specific data model for a determined problem
domain while
A DATA MODEL
Is
a relatively simple representation, usually graphical of more complex real
world data structures.
problem
domain can be defined as an area within the real world environment, with
well-defined scope and boundaries that is to be systematically addressed.
Model is an abstraction of a more complex real-world
object or event. And the main function is to help you understand the
complexities of real-world environment.
There
are some implementation ready data model that contain at least the components.
1. Adscription
of the data structure that will the end-user data
2. A set
of enforceable rules to guarantee will the end user data.
3. A data
manipulation methodology to support the real-world data transformation.
THE IMPORTANCE OF DATA MODELS
A well-developed data model can even foster improved
understanding of the organization for which the database design is developed.
Data models are a communication tool. Applications are
created to manage data different managers view data differently. Example. a
company president is likely to take a unusual view of the data because he or
she must be able to tie the company’s divisions to a common vision. A
purchasing manager in the same company is likely to have a more restricted view
of the data, as is the company’s inventory manager. Each department manger
works with a subset of the company’s data. The inventory manger is more
concerned about inventory levels while the purchasing manger is more concerned
about the cost of items and about personal business relationship with the
suppliers of those items.
DATA
MODEL BASIC BUILDING BLOCKS
Under data model basic building
blocks we have entities, attributes, relationship and constraints.
An entity is anything (a person, a
place, a thing or an event) about which are to be collected and stored. It can
represents a particular type of object in the real world. For example, a
customer such as John Smith.
An attribute:
Is
a characteristic of an entity. For example a customer entity would be descried
by attributes such as customer last name, customer first name, phone number,
address and the customer credit limit.
A Relationship:
Is
an association among entities. For example a relationship exists between
customers and agents that can be described as follows. an agent serve many
customers and each customer may be served by one agent. And under we have three
types of relationships:-
1.
One-to-many (1:m
or 1.) relationship a painter paints many different paintings but each one of
them is painted by only one-painter.
2.
Many-to-many
(m:nor..) relationship an employee many
learn many job skills and each job skill may be learned by many employees.
3.
One-to-one (1:1
or 1..1) relationship. A retail company’s management structure may require that
each of its stores be managed by a single employee.
A Constraint:
Is
a restriction placed on the data. It is important because they help to ensure
data integrity and it can be normally expressed in the form of rules.
Business Rule:
Is
a brief, precise and unambiguous description within a specific organization.
Examples
of business rules are as follows.
·
A customer may
generate may invoices
·
An invoice is
generated by only one customer
·
A training
session cannot be scheduled for fewer than 10 employees or for more than 30
employees
There
are some process of identifying and documenting business rules is essential to
database design for several reasons.
·
They help to
standardize the company’s view of data
·
They can be a
communications tool between users and designed
·
They allow the
designer to understand the nature, role and scope of the data.
·
They allow the designer
to understand business processes.
THE OBJECT – ORIENTED (00) MODEL
In the object –oriented data model (00DM) both data
and their relationship are contained in a single structure known as object. The
00DM is said to be a semantic data model because semantic indicates meaning.
COMPONENTS OF OBJECT – ORIENTED
(00)
·
An object is an
abstraction of a real world entity. An object represents only one occurrence of
an entity.
·
Attributes
describe the properties of an object for example. a PERSON object includes the
attributes name, social security number and date of birth.
·
Objects that
solve similar characteristics are grouped in classes.
·
Inheritance is
the ability of an object within the class hierarchy to inherit the attributes
and methods of the classes above it. For example two classes CUSTOMER and
EMPLOYER, can be created as subclasses from the class PERSON.
UNIFIED MODELING LANGUAGE (UML)
Is
a language based on object oriented concepts that describes a set of diagrams
and symbols that can be used to graphically model a system. UML class diagrams
are used to represent data and their relationship within the language UML
object –oriented system’s modeling language. The object oriented data model
advance were felt in many area, from system modeling to programming. The added
semantics of the object oriented data model allowed for a richer representation
of complex object.