conceptual and detailed sys design

7/28/2019 Conceptual and Detailed Sys Design

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Conceptual System Design


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In the conceptual design stage that the alternative overall

MIS designs are conceived and the best one is selected by

the system analyst in consultation with the

top management. The feasibility of meetingthe management objectives for the MIS is assessed

showing how the system will work at the high level is

drawn. Therefore, conceptual design is also known as

gross design; high level becomes the basis for

the detailed MIS design.


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Conceptual Design Steps

1. Defining problems in more details.

2. Refining the management objectives to set system

objectives.

3. Establishing system constraints.4. Determining information needs and their sources.

5. Developing alternative designs and selection one from

these various designs.

6. Document the conceptual design and preparing thereport.


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1. Define the problem-

The most important is that what are usually lacking

are clear definitions of the problems and the priority

system on the basis of problem is the main solution.Therefore, management must take the first step in

MIS design by formulating problems to be solved.

The problem can be solved by the iterative process.


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3. Establish System ConstraintsSystems constraints are also known as problem

boundaries or restrictions, constraints enable the designer

to stipulate the conditions under which objectives may be

attained and to consider the limitations that restricts the

design.Constraints may be viewed as a negative limitation on

systems design, there is a positive benefit also.

Establishing constraints will help to ensure that the design

is realistic.

Constraints may be classified as

External Constraints

Internal Constraints


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4. Determining Information needs

and sources

Information Needs :-For a good system design, a clear

statement of information needs is very important and

necessary.

Information Needs:- The information that can increase the

ability of managers in critical areas such as problems,

alternatives, opportunities and plans.


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The development of a concept of a system is a creative process

that involves synthesizing knowledge into some particular

pattern. The concept of an MIS would consist of the major

decision points, patterns of information flow, channels of

information and roles of managers and competitors.

It is obvious that each alternative concept of a system has

advantages and disadvantages. Sometimes one concept willdominate all others by major criteria.


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6. Document the best design

Sufficient information has been accumulated to begin a more

detailed description of the system concept. The manager should be involved to the extent that the system

provides the information required, the designer is concerned

with the nature of the materials and equipment as well as with

technical processing considerations.


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Design Methods

There are a no. of methods for designing information systems.

Following is a brief description of some of the popular

methods.

Problem Partitioning

Structured Design

Top-Down Design


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Problem Partitioning

The method is based on the principle of divide and

conquer. In this method, instead of solving the entireproblem at once, the problem is divided into small

manageable parts that can be solved separately.


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Structured Design

In this method, a structured chats is created , which

can be used to implement the system. The chart

depicts modules defining each module by the specific

function. Various tools like flow-charting , data flow

diagrams, structure charts, structured English, etc. are

used in a structured design.


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Top-Down DesignThe top-down design is based on the concept of a

system which suggests that a system consists of sub-

system, which have sub-system of their own. In otherwords, a system may be termed as a hierarchy of sub-

systems, the highest level sub-system corresponding

to the total system.


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Detailed System Design


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detailed system design is to prepare a

blue print of a system that meets the

goals of the conceptual system design

requirements.


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Detailed system design involves the following phases.

Project Planning and control

Involves the User

Define the Detailed Sub-SystemsInput/output Design

Feedback from the User

Database Design

Procedure DesignDesign Documentation


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Project PlanningIn order to ensure an effective and efficient design of

the MIS, it is very important that a detailed design

process should in itself be considered a complete

project. Some of the main points which are importantin planning and control of a detailed design are given

below.

Project Planning

Project Control


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Formulate the project Objectives.

Define the project task.

Prepare a network diagram of all events andactivities so as to specify sequential and parallel

events.

Schedule the work as per the requirements of the

user.

Prepare a budget for the project.


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Get a feedback of the actual performance of the

project with respect to time, cost and work of the

project and compare it with schedules, budgets andtechnical plans.

Take corrective action where required so as to

maintain control.

Project Control


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Involve the User

System designer must inform the users regarding the

new information system being developed and gain

their support and acceptance. It is also important to

take users in confidence so as to obtain information forthe design of the system. This will also help managing

resistance to change and would ensure successful

implementation of the system.


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Detailed Sub-System DefinitionIn detailed system design, every system needs to be broken down to

ascertain all activities required and their respective inputs and

outputs. In some of the cases, sub-systems are broadly defined in

the conceptual design phase, but at this stage they are specifically

defined to work out every detail concerning the sub-system,

Decomposition of the system to operational activities in general iscarried out as follows.

System

Sub-system

Functional ComponentTask

Sub-task

Operation element


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Wherever needed, integration of activities into a

sub-system may be done on the basis of any one or

more of the following common features.

Common functionsCommon techniques or procedures

Logical flow relationships

Common outputs or inputs


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Output/Input Design

As the main purpose of MIS is to provide information to aid

decision-making, to the user, output/input is one of the most

important characteristics of the information system. As

decisions are based on the output from the system and inputto the system, system designers must give this phase the

attention it deserves. The following paragraph will highlight

the key point to be considered while preparing output and

input design.


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Output design

The term output implies any information printed or

displayed, produced by an MIS. At this stage, the following

activities take place.

Specific outputs which are required to meet the informationneeds are identified.

Methods for presenting information are selected, and

Reports, formats or other documents that act as carrier of

information, produced by an MIS, are designed.


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Objectives of Output Design

It should provide information about the past, present or future events.

Outputs at the operational control level provide information of the past and

present events, whereas outputs which are required at the strategic planning

level include information on the future projections.

It should signal important events, opportunities and problems. For example,exceptional reports indicate such happenings.

It should trigger an action in response to some event. A set of rules is pre-

defined for such a trigger. For example, an order is prepared when inventory

reaches a certain level.

It should confirm an action as a result of some transaction. For example,

printing a receipt upon receiving the telephone bill.


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Presentation of Output

Details dominate the contents

Contents are classified in groupsTotal are to be drawn and comparisons are to be

made.


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Output Design SpecificationsPaper size: The designer must specify the size of the paper to be

used for the output, e.g. A4 size, A3 size, etc., or 9.5x11 inches,

11x14.7/8 inches or 8x14.7/8 inches etc.

Special Forms: Output can be designed on the pre0printed form

where standard print headings/titles, etc., are required.


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Sl. No. Item code Qty Ordered

Sigma Industries Ltd.

Purchase order


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Multiple Copies of Output: When more than one copy is required from thesystem, multiple copies are to be produced. This can be achieved by using

multipart forms. Multiple papers are available in carbon and carbonless forms.

Turnaround Documents: The output may be designed as a turnaround document,

if the organization uses optical scanners for reading data from the forms. Thus, ina turnaround document, the output later comes back as an input document.

Output layout: the arrangement of items on the medium is known as an output

layout. The layout design acts as a blueprint that guides the programmer in the

development of codes.


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The output layout should have the following.

Headings and date

Data and detailsSummaries and totals

Page title, number and date

Notes and comments

Column heading and data type. Designers usually use N (n) for numeric data

type and X (n) for alpha data type,-specifies the width of the column.

Total Pages N(2)

Emp. Code Name Amount Account No. Remark

X(4) X(20) N(8) X(4) X(25)

ABC Pvt. Ltd.

Salary Statement for the month N (2)


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Generally, output from a system is regarded as the

main determinant of the systems performance, yet

as already mentioned; outputs from the system are

affected by the inputs to the system. Therefore,

input design is equally important for the system

designer.

Input Design


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Control the volume of input data: try to reduce data

requirements and avoid capturing unnecessary data.

Constant and system- computable data should not be

captured.

Avoid processing delays during data entry: Automatingdata capturing may reduce this delay.

Avoid data entry errors: Checks in the data entry programs,

which are called input validation techniques may help.

Keep the process simple: the system should be kept assimple and easy to use as possible.

Objectives of Input Design


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Customer order Code: X(4) Date:

Sr. No. Item Code Qty. Ordered

1 X(4) N(4)

2

The input layout should contain the following.Heading and date of data entry.

Data heading and value.

Data type and width of the column.

Initials of data entry operator.

Fig. 3 illustrates an input layout design.

ABC Pvt. Ltd.

Customer Order Form

Input Layout


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Feedback from the User

Having specifically defined sub-systems, output and

inputs, the designers once again involves the users to get

feedback. This step will increase the acceptance of theMIS being designed. The system analyst should

demonstrate the proposed MIS to the users of the

system sub-system. This step will also reassure the top

management of the user organization that the detailed

design project is progressing as per plans.


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Database Design

A database is an orderly arrangement of all

the records related to each other. It serves

as a data resource for the MIS of anorganization. To have optimum

performance, storage and fast retrieval of

data, database design is an important phase

in the detailed design of a system.


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For designing a database the designer should keepthe following points in mind.

Identify all data tables and record types

Identify fields for each table, the key fields for

each table and relations between various tables.

Determine the data type and width for each field of

the tables.

Normalise the data tables.

Properly document data dictionary.


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Procedure Design

Procedures are the rules, standards or methods

designed to increase the effectiveness of the

information system. The procedures detail about

the tasks to be performed in using the system.

They serve as ready reckoners for the designers

as well as for the users.


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There is a wide variety of procedures, which include:

Data Entry Procedures: These are the methods designed for

data entry, e.g. data entry sequence.

Run-time Procedures: The actions to be taken by the users to

achieve the intended results, e.g. a procedure may instruct theuser to load printer with a specific size of paper.

Error-handling Procedures: these procedures help the user in

detecting and correcting errors.


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Security and backup Procedures: Through theseprocedures information is provided regarding actions

required to be taken to protect the system against damage.

Software Documenting Producers: The programmers get

instructions on how to document the programs.

In designing procedures, designers should:Understand the purpose and quality standard of each

procedure

Develop a step-by-step direction for each procedures,

andDocument all the procedures.


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Design Documentation

Detailed design starts with the

performance specifications given by the

conceptual design and ends with a set ofdesign specifications for the

constructions of MISD. The outputs from

the detailed design.


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Design documentation of detailed design report, generally, consists

of-

System objectives

Design constraints

Inputs/outputs

Data filesProcedures (manuals)

Proposed system (a summary and detailed flow charts)

Input/output specifications

Program specificationsDatabase specifications

Cost of installation and implementation and

System test conditions.


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Conclusion

System analysis is carried out with the help of certain tools, usually

known as structured analysis tools. The main tool, which are used for

analyzing and documenting the system specifications are data flow diagram,

data dictionary, structured English, decision trees and decision tables.

The main objective of the system design is to produce system

specifications, which can then be converted into an information system for

use in the organization. However the system design is a creative activity and

is considered to evolve through two different levels of design, i.e. conceptual

design and detailed design. The system specifications, called the detailed

system design or logical system design provide all detail of inputs, outputs,

files, database, controls and procedures. For ensuring an effective, efficientand successful MIS, the system analyst must not rush through this phase,

rather each and every step must be undertaken very carefully to prepare a

meticulous system design.


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