SYSTEM AND MODELS


By
Praveen Ranjan Srivastava
Lecturer (Computer Science)
Banasthali Vidyapith (Deemed University)
Banasthali-304002 (Rajasthan)
Phone : 01438-228787
E-mail : spraveen@banasthali.ac.in / pra_ranjan@rediffmail.com
 


INTRODUCTION---: The term system is used in such a wide variety of ways that it is very difficult to give a appropriate definition for this term.

Though it is very difficult to define this term yet there are more than hundred definitions that are given but most of them seems to have a common thread.

WHAT IS A SYSTEM---: We can define a system as that a system is an orderly grouping of interdependent components linked together according to a plan to achieve a specific objective. Or we can say that A system is define as an aggregation or assemblage of object joined in some regular interaction or interdependence.

EXAMPLES OF SYSTEM--: We come into contact in our daily life as the transportation system, telephone system, and for over two decades the computer system.

Let us take a simple example of a system  . Consider a factory that makes and assembles parts into a product. Two major components of the system are the fabrication department making the parts and assembly department producing the products.  

A FACTORY SYSTEM

A purchasing department maintains a supply of raw materials and a shipping department dispatches the finished products. A production control department

Receive orders and assigns work to the other departments.

Every system has some constraints.

ENTITY---: The term entity will be used to denote an objective of interest of a system.

ATTRIBUTES---: The property of any entity is called attributes. There can, of course, be many attributes to a given entity.

ACTIVITY---: Any process that causes the change in the system.

STATE OF THE SYSTEM---: The state of the system will be used to mean a description of all the entities, attributes, and activity as they exist at one point in time.

CHARACTERISTIC OF A SYSTEM

Our definition of system suggest that are present in all systems

1>: Organization---: Organization implies structure and order. It is the arrangement of components that helps to achieve objectives. For example in the design of a business system the hierarchical relationship starting with the president on the top and leading down ward to the blue-collar workers represents the organization structure.

Organization structure---An example

2> Interaction--: Interaction refers to the manner in which each component function with other component of the system. In an organization . for example purchasing must interact with production, advertising with sales.

3> Interdependence--: Interdependence means that the parts of organization or computer system depend on one another. One  subsystem depends on the input of another subsystem for proper functioning that is, the output of one subsystem is the required input for another subsystem.

4> Integration--: Integration refers to the holism of the system. Integration is concern with how a system is tied together. The parts of the system work together within the system even though each part perform a unique function. Successful integration will produce a synergistic effect and greater total impact than if each component works separately.

5> Central Objective---: Central objective may be real may be stated. The important point is that a user must know the central objective of a computer application early in the analysis for a successful design and conversion.

ELEMENTS OF THE SYSTEM

1> Output and Inputs--: Output are those elements that enters into the system for processing. While on other hand input are those which we obtain after the processing from a system.

2> Processor--: The processor is the element of the system that involves the actual transformation of input into out put.

3> Control--: The control element guides the system. It is the decision making subsystem that control the pattern of activities, governing the input, processing and output.

4> Feedback--: Control in the dynamic system is achieved by feedback. Feedback measures output against a standard in some form of cybernetic procedure that includes communication and control.

5> Environment--: The environment is a "suprasystem" within which an organization operates. It is the source of external elements that impinge on the system.

6> Boundaries and Interfaces--: A system should be defined by its boundaries –the limits that identify its components, processes and interrelationship when it interface with another system.

Inputs and outputs in a business Operation


SYSTEM DEVELOPMENT LIFE CYCLE

To understand system development. We need to recognize that a candidate system has a life cycle. There are different steps in the system development life cycle.

1> Recognition of need—What is the problem?---: We must know what is the problem before it can be solved. The basis for a candidate system is recognition of a need for improving an information system or procedure.

2> Feasibility study--: Feasibility study is the test of a system proposal according to its workability, impact on organization, ability to met the user needs, and effective use of resources.

3> Analysis---: Analysis is the detailed study of various operations performed by a system and their relationship within and outside the system.

4> Design--: This is the most creative and challenging phase of the system life cycle. The first step is to determine how a output is to be obtain and in which format. Second. Input data and masters files have to be designed to meet the requirements of the proposed output. The operational phases are handled through program construction. Finally, details related to the justification of the system and an estimate of the impact of the candidate system on the user and the organization are documented and evaluated by management as a step towards implementation.

STEPS IN SYSTEM DESIGN

5> Implementation--: It is primarily concern with user training site preparation, and file conversion.

6> Post-Implementation and maintenance--: After the installation phase is completed and the user staff is adjusted to the change created by the candidate system evaluation and maintenance begin.

Types of system--:

1> Continuous system---: Continuous systems are those in which all the activities that occur are predominantly smooth.

2> Discrete system--: Discrete system are those in which all the activities that occur are predominantly discrete.

SYSTEM MODELING

MODEL---: We define a model as the body of information about a system gathered for the purpose of studying the system. There is no unique model for the system i.e. if we have a system then we can construct a number of model for that system.

Types of models--: 

Physical Model--: Physical models are based on some analogy between such systems as mechanical and electrical or electrical and hydraulic, In a physical model of a system the system attributes are represent by such measurements as a voltage or position of the shaft. The system activities are reflected in to the physical laws that drive the model.

Mathematical Model --: Mathematical model use the symbolic notation and the mathematical equation to represent the system. The system attributes are represented by variables and activities are represented by mathematical function that interrelate the variables.

Static Model--: Static models can only show the values that system attributes take when the system is in balance.

Dynamic Model --: Dynamic model follows the changes over time that result from the system activities.

CORPORATE MODEL

We will illustrate the interaction that occur in the system by looking at the model of corporation. The model of this nature is called corporate model , and are used by many corporation to help in the various aspects of planning there operations. There main use is in helping to understand that what condition will prevail under the different sets of assumptions.

There are three main segments in the corporate model.

Major segments of corporate model

1> Environment Segment---: The corporation as a whole , operates within an environment.  It includes all those factors influencing the corporation that are not under in direct control.

The environment segment

Here the major element is the market model. Demand is the main output of this model. Two major inputs are the price and the supply of the product. Several other   factors can influence the market. One chosen here is the national economy, the population that purchase the product and competition from the other producers.

2> Plant Segment---: It provides the means for the production.

The main input is the amount of the labor and the machinery assigned for the production. The main output is the supply of the product. Production will be influenced by economic factors , national economy and world economy. If a

The production segment

National economy model is to be include, therefore it will interact with the production model. The world economy might also be important, if the cost of imported raw material has to be considered, or if any of the production facilities located overseas. Of course, if the product is sold overseas, the world economy model will also interact with the market model.

3> Management Segment--: Management segment represent the policy- making aspects of the corporation.

The management segment

The main inputs are the demand for the product, and the capital investment to be made in the business. The main out put are the price to be set and the profit to be expected. A pricing model   sets the price, and financial model decide how the investment capital is to be divided between labor and machinery.

Another activity of the management is to predict the future demand for the product. A forecasting may be needed to reflect the way the predictions to be made.

Both the national and the world economic conditions could influence the financial model through their effect on the money market.

PRINCIPLES USED IN MODELING

1> Block building--: The description of the system should be organized in a series of blocks. The aim of constructing the blocks is to simplify the specification of interaction within the system. Each block describe the part of the system depends upon few input variables and result some output variables.

2> Relevance--: The model should include only those aspects of the system that are relevant to the study objective. As an example, if the factory system study aims to compare the effect of the different operating rules on efficiency. It is not relevant to considering the hiring of employees as an activity. While relevant information may not do any harm. It should be excluded because it increases the complexity of the model and cause more work in solving the model.

3> Accuracy--: The accuracy of the information gathered for the model should be considered. For example in the aircraft system the accuracy with which the movement of aircraft is describe depends upon the representation of the airframe.

4> Aggregation--: A further factor to be considered is the extent to which the number of individual entities can be grouped together into the large entities. The general manager of the factory may be satisfied with the description that has been given. The production control manager, however will want to consider the shops of the departments as individual entities.
 


Praveen ranjan srivastava
Lecturer (Computer Science)
Banasthali Vidyapith (Deemed University)
Banasthali-304002 (Rajasthan)
Phone : 01438-228787
E-mail : spraveen@banasthali.ac.in / pra_ranjan@rediffmail.com
 

Source : E-mail February 26, 2004

 

B A C K

 

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