System Engineering:Analysis And Design

Chapter - 8

System Concepts

• Provides a meaningful framework for describing and understanding the features and functions of the subject.

• It is arranged with some logical governed by rules, regulations, principals and policies

• A system may have single input and multiple outputs or several inputs and outputs.

• Eg. Business System has several inputs and multiple objectives, such as sales, profit service and growth.

Cont….

• The environment influences the choice of inputs, the method of processing, and the nature and contents of the outputs.

Input Process Output

Filter

Environment

Fig: Generalised Model of a System

Systems Control

• The device that measures the output is called a censor.

• Set the standard or norm of the output as an index of the system performance.

• The sensor measures the output and compares it with the standard.

• System provides a feedback to continue the operations.

Control System Model

Input Process Output

Sensor

Comparison Unit

Standard

Corrective Unit

Channels of Feedback

Cont…

• Info. Sys. are designed in a particular environment of business, industry and management.

• When the environmental factors or the input changes, the system is under a stress.

• Stress beyond a limit affects the other system elements which in turn affects the achievements of the goal.

• Unmanageable stress leads to a system failure

Control System Model for Data Processing

Input Data

Use of Program for Processing

Computed Result

Summary of Results

Compare Results

Desirable or Known Summary

of Results

Corrective Unit Feedback

Change the program if Necessary

Va

lidate

D

ata If

Ne

cessary

MIS Model of Quality Assurance

Date on Measures of

Quantity

Manufacturing Process

Analysis of Quality Data

One Measure of Quality

Tools to Compare

Quality Control Limits

Corrective Unit Feedback

Action to Correct the Process of Manufacturing

MIS and Support to BusinessSystem Components

Business System MIS

Inputs Raw Materials, Plant and Machinery, Selling arrangements, Accounting

Data from transactions of purchase, production and sales, receipts and payments

Process

Outputs

Sensor Comparison Unit

Standard Feedback

Corrective Unit

Types of System

• System is defined and determined by its boundaries and objectives.

• Smaller systems together makes a large system and a large system can be split or decomposed into subsystems up to a certain level.

• The decomposition can be in a serial form or it could be in a matrix form.

• In any system the inputs are transformed into the output by the process.

• If the process of input transformation is not visible and understandable then we say that the system is a black box and the process is not transparent.

Subsystems in Serial Order

Manufacturing good

Subsystem 1

Quality Control

Subsystem 2

Marketing good

Subsystem 3

Subsystems Operating in Matrix OrderManufacturing good

Subsystem 1

Quality Control

Subsystem 2

Marketing good

Subsystem 3

Accounting good

Subsystem 4

Systems Classification• Deterministic : When the Input, Process and Outputs are

known certainly.– Eg: Accounting System.

• Probabilistic : When the Output can only be predicted in probabilistic terms.– Eg: Demand Forecasting System.

• Closed System : Functioning in isolation from the environment. Doesn’t have any exchange nor influenced by the environment.– Eg: Stock Management, Attendance System, Manufacturing System

• Open System : Systems which are required to respond to changes in the environment.– Eg: Marketing, Communication and forecasting system.

Handling System Complexity

• Factorization: – View the system as an assembly of subsystems,

each with a clear definition of the boundaries, interfaces and their connectivity.

– The subsystems then are put in the hierarchical order to provide a structural view showing the development path to the designer.

• Simplification:– Clustering the subsystems together.– Handling all the subsystems together with their

interconnections.

Method of Simplification

• Identify the subsystems which have to be together for the functional ‘cohesion’.

• Form a cluster of these subsystems and identify interconnections in this cluster.

• Form a cluster of the remaining subsystems.

• Connect the clusters with an interface.– Eg. Material Management System

Material Management System

A. Procurement System

B. Purchase Order follow up System

C. Receipts Accounting System

D. Material Requirement Planning System

E. Material issue requisition System

F. Bill Passing and Payment System

G. Inventory control System

Subsystems Interconnection

A C D F

B E G

Formation on Clusters on the Basis of Managerial Function

A

B

F

Cluster 1

Purchase Function

C

E

D

G

Cluster 2 Stock Accounting Function

Cluster 3 Material Planning

and Control Function

Decoupling of Subsystems’ Cluster by Stock Information Interface

A

B

F

C

E

D

G

Purchase

Information

Stock

Information