PPT15 by qingyunliuliu


									Chapter 15
Designing Accurate
Data-Entry Procedures

     Systems Analysis and Design
               Kendall & Kendall
                    Sixth Edition
Major Topics
• Data entry
• Effective coding
• Types of codes
• Guidelines for coding
• Validation methods
• Check digits
• Ecommerce accuracy
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.

Codes and Coding
  Coding helps efficiency because:
  • Data that are coded require less time to
  • 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.

Purpose of Coding
 Besides providing accuracy and
 efficiency, coding does the following:
  • Keeps track of something.
  • Classifies information.
  • Conceals information.
  • Reveals information.
  • Requests appropriate action.

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.

Simple Sequence Code
• Identifies 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
• No relation to the data itself

Alphabetic Derivation Codes
• A commonly used approach in
  identifying an account number
• See figure 15.2, for example, where the
  code becomes the account number

Alphabetic Derivation Codes
  • First five digits come from the first five digits of
    the subscribers zip code.
  • Next three are the first three consonants in the
    subscribers name.
  • Next four numbers are the street address.
  • Last three make up the code for the magazine.

Advantages of Alphabetic
Derivation Codes
  Advantages are:
  • 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

Disadvantages of Alphabetic
Derivation Codes
  Disadvantages are:
  • 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.

Classification Information
• Coding affords the ability to distinguish
  between classes of items.
• Classes must be mutually exclusive.
• Classification Codes are used to
  distinguish one group of data with
  special characteristics from another

Classification Information
• They consist of either a single letter or
  a number.
• Codes are shorthand way of describing
  a person, place, thing, or event.
• Classification codes are listed in
  manuals or posted so that users can
  locate them easily.

Classification Codes
• Use a single letter for a code.

Classification Codes Problems

Block Sequence Codes
• An extension of the sequence code
• Advantages
  • Data are grouped according to common
  • Simplicity of assigning the next available
    number (within the block) to the next item
    needing identification
  • Can do inquiries on code beginnings
Block Sequence Code

Cipher Codes
• Codes may be used to conceal or
  disguise information.
• Cipher Codes is the direct substitution
  of one letter for another, one number
  for another, or one letter for a number.

Cipher Codes

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.

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

Significant Digit Subsets
• Can do inquiries on portions of the code.
  • Look for matching red items, other size 10
    items, other maternity, or similar dresses

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 is
•   Using a combination of letters and symbols
    affords a clear way to code a product so that
    the code is easily seen and understood.

•   Unicode is used to store glyphs or symbols
    representing syllables or whole words.
•   Used for languages that are not Western
    alphabetic (Latin characters)
•   Stores 65,535 characters
•   Viewed using an input method editor
•   Represented using the &#hhhh where hhhh
    represents hexadecimal notation
•   Example: &3x3053 for the Japanese syllable

Function Codes
• Codes are often necessary for
  instructing either the computer or the
  person about actions to take.
• Function codes are short numerical or
  alphabetic codes used to spell out
  precisely what activities are to be

Guidelines for Coding
•   Guidelines for coding are:
    • 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.

Keep Codes Concise
• Overly long codes mean more
  keystrokes and consequently more
• 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.

Keep Codes Stable
 Stability means that the identification
 code for a customer should not change
 each time new data are received.

Make Codes That are Unique
• Codes should be unique.
• Make a note of all codes used in the
• Do not assign the same code number or
  name to the same items.

Allow Codes to be Sortable
• Codes must be sortable.
• For example: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

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.
Keep Codes Uniform
 Follow readily perceived forms most of
 the time
  • Avoid using the codes MMDDYY in one
  • YYDDMM in a second
  • MMDDCCYY in a third; CC - century

Allow for Modification of Codes
• The system will evolve over time.
• The coding system should be able to
  encompass change.

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.

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.

Effective Data Capture
 In order to assure the quality of data
  entered into the system, it is important
  to capture data effectively.

Guidelines for Effective Data

 Guidelines for effective and efficient
 data capture are:
  • 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.

Data-Entry Methods
  Data-entry methods include:
  • Keyboards.
  • Optical character recognition.
  • Magnetic ink character recognition.
  • Mark-sense forms.
  • Bar codes.
  • Intelligent terminals.

Bar Code Example

Validation Overview
• To assure data quality, errors should be
  detected during input, prior to
  processing and storage.
• Two possible ways to validate inputs
  • Validation of input transactions.
  • Validation of input data.

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
  • Asking the system to perform an
    unacceptable function.

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.

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.

Check Digits (Continued)
• 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

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.

Check Digit General Method
Remaining Steps
• Compute the check digit by taking the
  modulus number and subtracting the
  • Subtract again if greater than 10.
• Add check digit to the end of the
• Use this new code for data entry and let
  the computer validate the code.

Modulus 11 Arithmetic Method

The Process of Validation
• Check first for missing data.
• Then check the syntax: the length,
  class, and composition.
• Next check the semantics: the meaning
  of the data:
  • Limit.
  • Range.
  • Check digit.

Regular Expressions
• Use a pattern for validation.
• Symbols represent the type of data.
• Example: Email validation.


Regular Expression Codes

Ecommerce Accuracy
 Ecommerce environments have increased
  accuracy of data because:
  • Customers generally enter data themselves.
  • Data entered by customers are stored for later
  •   Data entered at the point of sale are used
      throughout the order fulfillment process.
  •   Information is used as feedback to customers.


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