PPT15 by qingyunliuliu

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									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
                          15-2
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.

                                           15-3
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.

                                               15-4
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.

                                          15-5
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.

                                   15-6
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



                                            15-7
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




                                      15-8
Alphabetic Derivation Codes
(Continued)
  • 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.




                                                       15-9
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
    account.


                                              15-10
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.




                                            15-11
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


                                         15-12
Classification Information
(Continued)
• 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.

                                         15-13
Classification Codes
• Use a single letter for a code.




                                    15-14
Classification Codes Problems




                            15-15
Block Sequence Codes
• An extension of the sequence code
• Advantages
  • Data are grouped according to common
    characteristics
  • Simplicity of assigning the next available
    number (within the block) to the next item
    needing identification
  • Can do inquiries on code beginnings
                                           15-16
Block Sequence Code




                      15-17
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.




                                       15-18
Cipher Codes




               15-19
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.




                                        15-20
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.



                                          15-21
Significant Digit Subsets
(Continued)
• Can do inquiries on portions of the code.
  • Look for matching red items, other size 10
    items, other maternity, or similar dresses




                                                 15-22
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
    mnemomic.
•   Using a combination of letters and symbols
    affords a clear way to code a product so that
    the code is easily seen and understood.

                                              15-23
Unicode
•   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
    ko

                                            15-24
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
  accomplished.


                                       15-25
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.

                                         15-26
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.

                                      15-27
Keep Codes Stable
 Stability means that the identification
 code for a customer should not change
 each time new data are received.




                                      15-28
Make Codes That are Unique
• Codes should be unique.
• Make a note of all codes used in the
  system.
• Do not assign the same code number or
  name to the same items.




                                         15-29
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

                                             15-30
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.
                                          15-31
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



                                          15-32
Allow for Modification of Codes
• The system will evolve over time.
• The coding system should be able to
  encompass change.




                                        15-33
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.




                                         15-34
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.

                                           15-35
Effective Data Capture
 In order to assure the quality of data
  entered into the system, it is important
  to capture data effectively.




                                        15-36
Guidelines for Effective Data
Capture

 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.

                                            15-37
Data-Entry Methods
  Data-entry methods include:
  • Keyboards.
  • Optical character recognition.
  • Magnetic ink character recognition.
  • Mark-sense forms.
  • Bar codes.
  • Intelligent terminals.

                                          15-38
Bar Code Example




                   15-39
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.

                                         15-40
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.


                                          15-41
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.

                                            15-42
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.

                                        15-43
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



                                      15-44
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.

                                       15-45
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.

                                         15-46
Modulus 11 Arithmetic Method




                          15-47
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.

                                       15-48
Regular Expressions
• Use a pattern for validation.
• Symbols represent the type of data.
• Example: Email validation.

[A-Za-z0-9]\w{2,}@[A-Za-z0-9]\w{3,}\.[A-Za-z]{3}/




                                                15-49
Regular Expression Codes




                           15-50
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.



                                                      15-51

								
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