An Introduction to Database Management Systems Schemas – Pros and Cons

The database management system is built up of different kinds of data. This is where database administrators deploy the use of data abstraction.

The goal here is helping the user better understand the structure, retrieve data, and decrease complexities in operations. Data abstraction comprises of three fundamental levels, and they are:

• The Internal Level. This is the first level. The access path and the physical storage is done at this level. 

• The Logical or the Conceptual Level. This level deals with the constraints and the structure of the whole database.

• The View or the External Level. This level of the system describes the user’s diverse views.

Given below is a detailed overview of the three critical levels of database management schemas.

1. Internal level of database management systems schema

This implies the database system physically. It represents the whole database at its lower levels and has several occurrences of internal records.

It is known as the “stored record” as well. 

Internal schema facts 

• This level is its lowest level for data abstraction

• It aids you to keep data that represents the system as a whole. It is similar to storing information in the disk as records of the data. 

• The user gets an insight into the stored data and how the information has been stored

• It does not deal with any physical device of the system. It can view any of this device like a library of pages in a physical form.

2. Conceptual level schema 

This level is the database as a whole system of information for the collection of users. It hides data associated with physical structure storage.

This schema describes different types of data, the relationships, entities, and more. This is the level of logic that is between the view of the physical storage and user.

The view of the database that is conceptual in nature. The salient facts about the conceptual database are as follows:

• It defines all the entities of the database along with their relationships and attributes 

• It has all the information about its integrity and safety

• At this level, the system becomes accessible to the user should be contained inside or be derived at its physical levels. 

3. External level schema 

This is that portion of the whole database the user wants to see. The information of the database unrelated to a user is concealed. There can be a specific amount of views for the database. 

Every external view has been defined with a schema. It consists of several definitions of different kinds of external records for a specific view.

The external view refers to merely the database content that has been seen by the specific user.

For instance, if a user is a member of the marketing team of any company, he will only be able to see sales related information or data. 

Salient facts about the external schema 

• The external schema refers to the data seen by specific end-users only

• This level will have external schemas as well. 

• The external schema level is closest to the user

• It is required for specific users and conceals information from a particular user community.

What is the objective of three Levels or the schema of a database?

Experts from reliable databases the systems management company, RemoteDBA.com, say these three levels of a database have a goal.

The following are the objectives of the schema of a database in three levels:

• The same data should be accessible to every end-user and able to view a customized picture of the information.

• The end-user does not have directly deal with the details of the physical storage details.

• The database management system the administrator should have the ability to make changes to the database without interrupting the view of the current users 

• The internal database structure should remain unaltered when these changes are done to the elements of storage at its physical level. 

Benefits of a database schema

The following are the main advantages of a database schema: 

• It is simple for you to take care of the independent data of the unit physically. 

• You get quick migration to those environments that are graphical in nature and new

• The DBMS architecture permits you to alter the presentation levels without interfering the rest of the layers

• You can use different developers as each of the tiers are separate from one another. 

• Security is high as the end-user does not have access to the business logic of the database directly

• You will not suffer from data loss if one tier fails. The database is always secure because the rest of the tiers can be accessed without hassles. 

The business process schema

The business processes schema species what data are collected about business cases and how business cases are processed irrespective of particular business policy or work organization currently effective.

Following an object-oriented approach, we use Object/Behaviour diagrams (OBDs) for the conceptual design of the business process schema.

OBDs have been originally introduced for the design of object-oriented databases.

It should be noted that any other object-oriented design approach, like UML, may be used as well for modeling the business process schema.

Since OBDs have already been introduced elsewhere, we describe herein only a few basic concepts which are needed to illustrate how elements at different levels of the three-schema architecture are interconnected.

A business process schema consists of a set of business object types, whose instances represent business cases.

Using OBDs, the structure and behavior of the instances of a business object type are denied by an object diagram and a behavior diagram, respectively. 

1. The structural business process schema

The structure of business objects is denied by object diagrams, which are comparable to class diagrams in UML and Entity-Relationship diagrams.

An object diagram depicts an object type by a rectangle. A shaded horizontal bar shows the name of the object type, nested ovals show attributes, and nested rectangles relationships.

Single-line and double-line borders of rectangles indicate single-valued and multi-valued relationships, respectively.

2. The behavioral business process schema

The behavior of instances of a business object type is depicted by a behavior diagram, which is usually split for readability into a life-cycle diagram, several activity-specification diagrams, and several activity-realization diagrams.

The A life-cycle diagram provides an overall view of a business process by depict-ing the states in which a business case may reside and the activities that may be performed on the business case.

An activity may be invoked on a business case if the business case resides in every state of the activity (or more precisely, if the object identifier of the object that represents the business case belongs to every state of the activity).

Upon the invocation of the activity, the object is removed from all prostates and moved into an implicit activity state named after the activity.

After the successful execution of an activity, the object is removed from the activity state and moved into every post-state of the activity.

Activities are shown by small rectangles with the activities’ names on their top, states are depicted by rectangles with a trapezium on their top.

Are there any disadvantages to the database management system schema?

Though the database management system schema architecture has several advantages, it has its share of cons.

The following are the key disadvantages of the database management system schema:

• This complete database schema can be very a complex structure that is complex in nature to understand by everyone.

• It isn’t easy to organize and take care of

• The physical segregation of all of these levels affects the database’s performance at times. 

When it comes to the database management system schema, professionals sum up by saying you must first remember there are three levels of database abstraction: the internal level, the logical or the conceptual Level, or view or external level.

Internal schema is actually part of the physical part of the data system. Its conceptual schema refers to the entire database for a group of end-users and is its structural portion.

The external schema refers to that portion of the database that the user wishes to view in the system.

Note that the database management system architecture has a significant advantage as it permits you to create any change to levels of presentation of the database without the fears of affecting the rest of the layers of the database schema.