Introduction to System Modelling

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System modelling

System modelling is also called system model. System modelling is a process. This process develops the overall structure of a system. This process develops an abstract model of the system, with each model presenting a different view or perspective of the system. Many models are involve in system modelling, that is, it is made up of many models. All the models in the system model are represent in a graphical way (in the form of pictures). To represent the complete model or structure of any system, we use graphical structure or graphical notation which is base on a language, this language is called UML (unified modelling language).

System modelling helps in understanding the functionality of the system and model by analyzing it. Which is use to communicate with the customer.

System perspective –

There are four types of system perspective in system modelling –

  • External perspective
  • Interaction perspective
  • structural perspective
  • Behavioural Perspective

External perspective 

External perspective is the perspective that is used to model or design an external environment of the system.

Interaction perspective 

An interaction perspective is a perspective where we model (design) the interactions between a system and its environment or between the components of a system.

Structural perspective 

A structural perspective is a perspective where you model the organization of a system or the structure of the data processed by the system.

Behavioural perspective – Behavioural perspective is the perspective where we design the dynamic behaviours of the system. And let’s see how it responds to events.


The full name of UML is unified modelling language. Which is a standard for representing real world objects in an object-oriented design methodology. That is, UML is a standard modelling language which contains a group of diagrams. Which helps developers in making models.

UML diagram types 

Here are five types of UML diagrams that represent system design or architecture for any organization.

Activity diagram 

Activity diagram shows the activities involved in a process or data processing.

Use-case diagram 

Use-case diagram shows the interaction between a system and its environment.

Sequence diagram 

What a sequence diagram is is that it shows the interaction between the system and the components of the system.

Class diagram 

Class diagram shows the object class in the system and the association between these classes.

State diagram 

State diagram shows how the system reacts to internal and external events.

Types of system models 

There are many types of system models, some of which are describe below –

  • data model
  • object model
  • Context model
  • behavioural model

Data model 

In the data model we represent how our data is moving from one module to another. Data modelling is a type of system model. In the data model, the flow of input, output and processing data is represent through graphical notation. It is also called E-R modelling or E-R Notation.

Different types of notation for data flow (data flow notation) 

Rectangle shape This shape is use to represent the external entities of any system.

Data store This shape is use to store many types of information or data in the data base.

Data process / circle This shape is use for processing any information or data in this notation.

Diamond shape / decision making diagram This shape is use to represent relationships between entities.

Arrow This shape is use to represent the movement of data left to right, right to left, top to bottom or bottom to top.

Perception (SCHEMA) of data model 

There are three types of perception to present the data model –

Physical perception in this, the database schema creates and checks how our database schema is related to each other.

Conceptual perception It is also called logical perception. In this we see how our data is being insert, deleted and updated.

External perception It is also called end user perception. In this we see how and in which environment our data is being process.

Object model 

Object model is a type of system model. In which all real-world problems are solve using objects. The object model describes the system’s objects, classes and the associations between them. In object model, complex projects can be develop easily with complete security. Classes are use to bind data information and their associated functions. In this, we keep irrelevant or unnecessary information hidden from end users.

Inheritance model 

In this model, information or attributes of one class are inherit from another class. A class from which information is inherit by another class is called super class and the class which inherits information from another class is called sub class.

Aggregation model 

In aggregation model we will show how classes are surround by other classes. In this model we will represent the relationship between classes.

Interaction model 

In this model we show how our data moves from one object to another. In interaction model, movement of data from one object to another is an important role of interaction model.

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