Information Modeling By means of Entity Relationship (ER) Method Part – 1
Introduction
An information modeling is an intangible illustration of the information arrangements which is necessary for a database. The information arrangements are consisting of the information objects, the relations among information objects, as well as the guidelines which controls he the actions on the objects. As the title suggests, the information modeling emphases on what information is needed as well as by what means it must be arranged rather than what actions will be done on the information. In the direction of using a common comparison, the information modeling is equal to an engineer’s construction plans.
An information modeling is liberated in terms of hardware and / or software constrictions. Instead of attempts to signify the information as a database would understand it, the information modeling emphases on demonstrating the information as the end user perceives it in the "Actual World". It works as a connection among the ideas which frame the actual world actions as well as procedures plus the physical demonstration of those ideas in a database.
Approach
There are two (2) main approaches castoff to form an information modeling:
1. The Entity Relationship (ER) method and
2. The Object Model (OM) method.
In this article we will be discussing only the Entity Relationship (ER) method.
Information Modeling in the Perspective of Database Design
Database design is demarcated as: "design the logical as well as the physical arrangement of one (1) or more (N) databases to provide spaces for accommodating the data which is wanted by the end users in a business for a distinct group of systems". The design method approximately has five (5) stages:
1. Planning as well as analysis
2. Theoretical design
3. Logical design
4. Physical design
5. Application
The information modeling is one (1) portion of the theoretical design procedure. The other, classically is the practical modeling. The information modeling emphases on what information must be kept in the database while the practical modeling focuses on by what means the information is handled. In the direction of putting this in the setting of the relational database, the information modeling is castoff to plan the relational tables. The practical modeling is castoff to plan the enquiries which will access as well as execute actions on those tables or relations.
Constituents of an Information Modeling
The information modeling acquires its inputs from the plan and analysis phase. In this situation the person who carry out the modeling and the specialists together, gathers data about the necessities of the database by means of studying current documents as well as questioning end users.
The information modeling has two (2) results. The 1st is an Entity Relationship (ER) diagram which signifies the information arrangements in a pictographic arrangement. For the reason that the illustration is simply learned, it is valued tool to link the modeling to the end users. The 2nd module is information documentation. This documentation defines the information entities, associations, as well as guidelines mandatory for the database in details. The dictionary delivers the details needed by the database designer for creating the physical database.
Significance of Information Modeling
Information model is possibly the greatest efforts concentrated as well as time consuming portion of the development procedure. A common reaction of the experts is that an individual must not construct a database without a modeling in hand because an individual cannot construct a building without the blueprint of the house.
The aim of the information modeling is to guarantee that every information entities needed by the database are totally as well as exactly signified. For the reason that the information modeling practices are simply understood by the representations as well as normal semantic are used, it can be studied in addition to confirmed as accurate by the end users too.
The information modeling is comprehensive enough to be castoff by the database designers to practice it as a blueprint for constructing the physical database too. The data enclosed in the information modeling will be castoff to describe the relational tables or relations, primary as well as foreign keys, stored procedures (SPs), in addition to triggers. An inefficiently designed database will need more time in the long run. Devoid of cautious design an individual might form a database which neglects information essential for preparing some serious reports, creates output set which are inappropriate otherwise unreliable, as well as is incapable to put up modifications in the end user’s necessities.
The Entity Relationship (ER) Modeling
The Entity Relationship (ER) modeling was initially offered by Peter in 1976 as a method to join the network as well as relational database views. Basically quantifying the Entity Relationship (ER) modeling as theoretical information modeling which interprets the real world as objects in addition to relations. A straightforward factor of the modeling is the Entity Relationship (ER) figure which is castoff to visually signify data items. From the time when Chen penned his paper the modeling has been comprehensive and in the present day it is usually castoff for database design. For the database developer, the usefulness of the Entity Relationship (ER) modeling is:
· It maps fine to the relational model. The concepts castoff in the Entity Relationship (ER) modeling can with no trouble be converted into relational tables or relations.
· It is simple as well as stress free to realize with a least possible training. For that reason, the modeling can be castoff by the database developer to interconnect the design to the end user.
· Furthermore, the modeling can be castoff as a design blueprint by the database designer to apply information modeling in a particular Database Management Software (DBMS).
In the upcoming parts (Part 2 & Part 3) we will be discussing the Simple Concepts of Entity Relationship (ER) Model only. The structure of the parts is given below:-
· Objects or Entities (Part – 2)
· Distinctive Object or Entity Forms (Part – 2)
· Relationships (Part – 2)
· Columns or Attributes (Part – 2)
· Categorizing Relationships (Part – 2)
o Relationship Degree (Part – 2)
o Connectivity plus Cardinality (Part – 2)
o one to one (1 to 1) (Part – 2)
o one to many (1 to N) (Part – 2)
o many to many (N to N) (Part – 2)
o Course (Part – 3)
o Kind (Part – 3)
o Presence (Part – 3)
• Simplification Hierarchies (Part – 3)
• Entity Relationship (ER) Symbolization (Part – 3)