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Transcript of Chap19
Chapter 19Designing AccurateData-Entry Procedures
Systems Analysis and DesignKendall and Kendall
Fifth Edition
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-2
Major Topics
Data entry Effective coding Types of codes Guidelines for coding Validation methods Check digits Ecommerce accuracy
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-3
Quality Data-Entry Objectives
The quality of data input determines the quality of information output
Accurate data entry is achieved through four broad objectives:
Effective coding Effective data capture Efficient data capture and entry Assuring quality through validation
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-4
Codes and Coding
Coding helps efficiency because Data that are coded require less time to
enter Coding helps to reduce the number of
items entered Coding can help in sorting of data during
the data transformation process Coded data can save valuable
memory/storage space
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-5
Purpose of Coding
Besides providing accuracy and efficiency, coding does the following: Keeping track of something Classifying information Concealing information Revealing information Requesting appropriate action
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-6
Types of Codes Types of codes are
Simple sequence code Alphabetic derivation codes Classification codes Block sequence codes Cipher codes Significant digit subsets Mnemonic codes Function codes
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-7
Simple Sequence Code
Identify a person, place, or thing in order to keep track of it
A number that is assigned to something if it needs to be numbered
It has no relation to the data itselfOrder Number Product5676 Rocking Chair5677 Dining Room Table5678 Love Seat
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-8
Alphabetic Derivation Codes
A commonly used approach in identifying an account number
The code becomes the account number
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-9
Alphabetic Derivation Codes
First five digits come from the first five digits of the subscriber's zip code
Next three are the first three consonants in the subscriber's name
Next four numbers are the street address Last three make up the code for the
magazineCode Format of Code68506KND7533TVG 99999XXX9999XXX
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-10
Advantages of Alphabetic Derivation Codes
Advantages Can have zip code in front for sorting A requirement for bulk mailing A magazine subscription may be used
weekly for mailing Can verify a person calling about their
account
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-11
Disadvantages of Alphabetic Derivation Codes
Disadvantages Names like ROE - become RXX Street addresses like 12 OAK STREET
- code contains 1200 Changing name or address results in
the key field being changed
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-12
Classification Information
Coding affords the ability to distinguish between classes of items
Classes must be mutually exclusive Classification Codes Used to distinguish one group of data
with special characteristics from another
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-13
Classification Information
Consist of either a single letter or a number
A shorthand way of describing a person, place, thing, or happening
Classification codes are listed in manuals or posted so that users can locate them easily
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-14
Classification Codes
Use a single letter for a code
Code Tax Deductible ItemInterest Payments
Medical Payments Taxes Contributions Dues
Supplies
IMTCDS
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-15
Classification Codes Problems
Code Tax Deductible ItemInterest Payments
Medical Payments Taxes Contributions Dues
Supplies Subscriptions Computer Insurance Miscellaneous
IMTCDSBPNX
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-16
Block Sequence Codes
An extension of the sequence code Advantages
That the data are grouped according to common characteristics
The simplicity of assigning the next available number (within the block) to the next item needing identification
Can do inquiries on code beginnings
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-17
Block Sequence Code
Code Name of Software Package Type100 Netscape Browser101 Internet Explorer102 Lynx200 Access Database201 Paradox202 Oracle300 Word Word Processing301 WordPerfect400 Astound Presentation401 Micrograf Designer
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-18
Cipher Codes
Codes may be used to conceal or disguise information
Cipher Codes Direct substitution of one letter for
another, one number for another, or one letter for a number
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-19
Cipher Codes
Code Meaning B 1 L 2 E 3 A 4 C 5 H 6 M 7 I 8 N 9 D 0
GOLDEN’S202-395-40BIMC
Size 12$25.00
Style Code
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-20
Revealing Information
Sometimes it is desirable to reveal information through a code
Make the data entry more meaningful
Allows persons to view the code and understand what it means
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-21
Significant Digit Subsets
Used to describe a product via its membership in many subgroups
The advantage of using a significant-digit subset code is the ability to locate items that belong to a certain group or class
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-22
Significant Digit Subsets
Code Merchandise Described2023954010 Red maternity dress, style 395, size 10
202 Department (maternity)395 Product (dress style 395)40 Color (red)10 Size (size=10)
Can do inquiries on portions of the code Look for matching red items, other size
10 items, other maternity, or similar dresses
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-23
Mnemonic Codes
A mnemonic (pronounced nî-môn'-ïk) is a memory aid
Any code that helps data-entry person remember how to enter the data or
End user remember how to use the information
Uses a combination of letters and symbols
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-24
Function Codes
Codes are often necessary for instructing either the computer or the person about actions to take
Function Codes Spelling out precisely what
activities are to be accomplished is replaced by the use of a short numerical or alphabetic code
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-25
Guidelines for Coding
Guidelines for coding Keep codes concise Keep codes stable Make codes that are unique Allow codes to be sortable Avoid confusing codes Keep codes uniform Allow for modification of codes Make codes meaningful
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-26
Keep Codes Concise
Overly long codes mean more keystrokes and consequently more errors
Long codes also mean the information in the files will require more memory
If codes must be long, they should be broken up into subcodes
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-27
Keep Codes Stable
Stability means that the identification code for a customer should not change each time new data are received
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-28
Make Codes That are Unique
Assure that codes are unique Make a note of all codes used in
the system Do not assign the same code
number or name to the same items
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-29
Allow Codes to be Sortable
The codes must be sortable Problem date: MMMDDYY
First three symbols are the month as a three-letter abbreviation
Second two are the date as a number Last two digits are the year
Numerical codes are much easier to sort than alpha-numeric data
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-30
Avoid Confusing Codes
Avoid using coding characters that look or sound alike O (the letter oh) and 0 (the number zero) Letter I and the number 1 Letter Z and the number 2 Codes such as B1C and 280Z are
confusing Canadian Postal Code The code format is X9X 9X9
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-31
Keep Codes Uniform
Follow readily perceived forms most of the time Avoid using the codes MMDDYY in one
application YYDDMM in a second MMDDCCYY in a third; CC - century
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-32
Allow for Modification of Codes
The system will evolve over time The coding system should be able
to encompass change
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-33
Make Codes Meaningful
Effective codes contain information They should make sense to people
using them Meaningful codes are easier to
understand, work with, and recall
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-34
Using Codes
Codes are used In validation programs to ensure that only
valid codes have been entered In report and inquiry programs to display
code meanings In GUI programs to create drop-down lists This helps to ensure accurate data, since
the user sees the code and it’s meaning and can only select a code from the list
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-35
Effective Data Capture
In order to assure the quality of data entered into the system, it is important to capture data effectively
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-36
Guidelines for Effective Data Capture
Guidelines for effective and efficient data capture Deciding what to capture Letting the computer do the rest Avoiding bottlenecks and extra steps Starting with a good form Choosing a data-entry method
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-37
Validation Overview
To assure data quality, errors should be detected during input, prior to processing and storage
Two possible ways to validate inputs are: Validation of input transactions Validation of input data
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-38
Data-Entry Methods
Data-entry methods include Keyboards Optical character recognition Magnetic ink character recognition Mark-sense forms Bar codes Intelligent terminals
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-39
Problems With Input Data
Three main problems that can occur with input transactions are Submitting the wrong data to the
system Submitting of data by an
unauthorized person Asking the system to perform an
unacceptable function
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-40
Validation Methods
Validation methods include Test for missing data Test for correct field length Test for class or composition Test for range or reasonableness Test for invalid values Cross-reference checks Test for comparison with stored data
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-41
Check Digits
Check digits are used to validate a numeric field by performing a calculation on a part of the number and comparing the result with a digit stored within the number
Check digits help to detect Single digit miskey Transposition errors
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-42
Check Digits
There are several check digit methods: Modulus 10, “2-1-2” method Modulus 10, “3-1-3” method Modulus 11, arithmetic method Modulus 11, geometric method
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-43
Check Digit General Method
Start with the numeric code Choose the weighting method and
modulus number Multiply the digit by the chosen
weight Sum the new numbers Divide by the modulus number
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-44
Check Digit General Method Remaining Steps
Compute the check digit by taking the modulus number and subtracting the remainder Subtract again if greater than 10
Add check digit to the end of the number
Use this new code for data entry and let the computer validate the code
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-45
Modulus 11 Arithmetic Method
Number 2 9 6 4 5 Original numberWeights 6 5 4 3 2 29645Product 12 45 24 12 10
Sum of products = 103 Final numberDivide 103/11 = 9 remainder 4 296457Checkdigit = 11- 4 = 7
11 - 4 7
9 R 411 103
-994
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-46
Using Codes
Codes may be included in drop-down lists when using a GUI interface
This helps to ensure that the data entered are accurate, since the user sees both the code and it’s meaning and can only select a code from the list
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 19-47
Ecommerce Accuracy
Ecommerce environments have increased accuracy of data because Customers generally enter data themselves Data entered by customers are stored for
later use Data entered at the point of sale are used
throughout the order fulfillment process Information is used as feedback to customers