Bài giảng Systems Analysis and Design - Chapter 15: Designing Accurate Data Entry Procedures

Designing AccurateData Entry ProceduresSystems Analysis and Design, 7eKendall & Kendall15© 2008 Pearson Prentice HallLearning ObjectivesUnderstand the uses of effective coding to support users in accomplishing their tasksDesign effective and efficient data capture approaches for people and systemsRecognize how to ensure data quality through validationArticulate accuracy advantages of user input on ecommerce Web sites2Accurate Data-Entry ObjectivesEffective codingEfficient data captureEffective data captureAssuring data quality through validation3Major TopicsEffective codingTypes of codesGuidelines for codingValidation methodsCheck digitsEcommerce accuracy4Effective CodingData that are coded require less time to enterCoding helps to reduce the number of items enteredCoding can help in sorting of data during the data transformation processCoded data can save valuable memory and storage space5Human Purposes for CodingKeeps track of somethingClassifies informationConceals informationReveals informationRequests appropriate action6Keeping Track of SomethingSimple sequence codeAlphabetic derivation codes7Simple Sequence CodesA number that is assigned to something if it needs to be numberedNo relation to the data itselfFigure 15.1 Using a simple sequence code to indicate the sequence in which orders enter a custom furniture shop8Simple Sequence Codes (Advantages)Eliminates the possibility of assigning the same numberIt gives users an approximation of when the order was received9Simple Sequence Codes (Disadvantages)When you do not wish to have someone read the code to figure out how many numbers have been assignedWhen a more complex code is desirable to avoid a costly mistake10Alphabetic Derivation CodesA commonly used approach in identifying an account number Figure 15.2 Identifying the account of a magazine subscriber with an alphabetic derivation code11Alphabetic Derivation Codes (Disadvantages)When the alphabetic portion is small or when the name contains fewer consonants than the code requiresNames like ROE - become RXXSome of the data may change12Classification InformationAffords the ability to distinguish between classes of itemsMust be mutually exclusiveClassification codesBlock sequence codes 13Classification CodesUsed to distinguish one group of data with special characteristics from anotherCan consist of either a single letter or a numberA shorthand way of describing a person, place, thing, or eventListed in manuals or posted so that users can locate them easily14Classification CodesUse a single letter for a codeFigure 15.3 Grouping tax-deductible items through the use of a one-letter classification code15Block Sequence CodesAn extension of the sequence codeData are grouped according to common characteristicsSimplicity of assigning the next available number (within the block) to the next item needing identification16Figure 15.5 Using a block sequence code to group similar software packages17Concealing InformationCodes may be used to conceal or disguise informationCipher Codes18Cipher CodesThe direct substitution of one letter for another, one number for another, or one letter for a number19Figure 15.6 Encoding markdown prices with a cipher code is a way of concealing price information from customers20Revealing InformationSometimes it is desirable to reveal information to specific users through a codeMakes the data entry more meaningful for humansSignificant-Digit subset codesMnemonic codesUnicode21Significant-Digit Subset CodesUsed to help describe a product by virtue of its membership in many subgroupsPossible to locate items that belong to a certain group or classInquiries may be performed on a portion of the codeUseful for a marketing product22Figure 15.7 Using a significant-digit subset code helps employees locate items belonging to a particular department23Mnemonic CodesA mnemonic (pronounced nî-môn'-ïk) is a human memory aidAny code that helps the data-entry person remember how to enter the data or the user remember how to use the information is a mnemonicUsing a combination of letters and symbols affords a clear way to code a product so that the code is easily seen and understood24Figure 15.8 Mnemonic codes function as memory aids by using a meaningful combination of letters and numbers25UnicodeIncludes all standard language symbolsHas room for 65,535 charactersThe full set of Unicode characters are grouped by language and may be found at www.unicode.org26Requesting Appropriate ActionInstruct either the computer or the decision maker about what action to takeFunction codes27Function CodesShort numeric or alphanumeric codes used to spell out precisely what activities are to be accomplished28Figure 15.9 Function codes compactly capture functions that the computer must perform29General Guidelines for CodingBe conciseKeep the codes stableEnsure that codes are uniqueAllow codes to be sortableAvoid confusing codesKeep the codes uniformAllow for modification of codesMake codes meaningful30Be ConciseOverly long codes mean more keystrokes and consequently more errorsLong codes also mean that storing the information in a database will require more memoryShort codes are easier for people to remember and easier to enterIf codes must be long, they should be broken up into subcodes31Keep the Codes StableStability means that the identification code for a customer should not change each time new data are receivedDon’t change the codes in a mnemonic system32Ensure That Codes Are UniqueFor codes to work, they must be uniqueDo not assign the same code number or name to the same items33Allow Codes to Be SortableMake sure that users can do what you intend to do with the codes you createNumerical codes are much easier to sort than alphanumeric data34Avoid Confusing CodesAvoid using coding characters that look or sound alike35Figure 15.12 Combining look-alike characters in codes can result in errors36Keep the Codes UniformNeed to follow readily perceived formsKeep codes uniform among as well as within programs37Allow for Modification of CodesThe system will evolve over timeThe coding system should be able to encompass change38Make Codes MeaningfulEffective codes contain informationShould make sense to people using themEasier to understand, work with, and recall39Using CodesValidation programs Report and inquiry programs GUI programs 40Effective and Efficient Data CaptureDeciding what to captureLetting the computer do the restAvoiding bottlenecks and extra stepsStarting with a good formChoosing a data-entry method41Deciding What to CaptureData that change or vary with every transactionData that concisely differentiate the particular item being processed from all other items42Letting the Computer Do the RestRecording the time of the transactionCalculating new values from inputStoring and retrieving data on demand43Avoiding Bottlenecks and Extra StepsData are poured rapidly into the wide mouth of the system only to be slowed in its “neck” because of an artificially created instance of insufficient processing for the volume or detail of the data being enteredThe fewer steps involved in inputting data, the fewer chances there are for the introduction of errors44Starting with a Good FormWith effective forms, it is not necessary to reenter information that the computer has already stored, or data such as time or date of entry that the computer can determine automatically45Choosing a Data-Entry MethodKeyboardsOptical character recognitionMagnetic ink character recognitionMark-sense formsBar codesRFID46KeyboardsSpecial function keys to open programsKeys used to scroll and explore the WebKeys that can be programmed with macros to reduce the number of keystrokes requiredErgonomic keyboards and infrared or Bluetooth-enabled keyboards47Optical Character RecognitionIncreased speed Eliminates many of the time-consuming and error-fraught steps of other input devicesDecentralizes responsibility for quality data directly to the unit that is generating itThe transformation of faxes into documents that can be edited48Magnetic Ink Character RecognitionA reliable and high-speed method that is not susceptible to accepting stray marksIf it is required on all withdrawal checks, it serves as a security measure against bad checksData entry personnel can see the numbers making up the code if it is necessary to verify it49Mark-Sense FormsLittle training of entry personnel is necessaryA high volume of forms can be processed quicklyStray marks on form can be entered as incorrect dataChoices are limited to the answers providedDifficulty in capturing alphanumeric dataEasy to get confused and put a mark in an incorrect position50Bar CodesAffords a high degree of accuracy for data entrySaves labor costsAllows the automatic capturing of dataTracking of credit card purchases51Figure 15.17 Bar coding, as shown on this label for grocery product, affords highly accurate data entry. Used with the permission of the Uniform Code Council, Dayton, Ohio52RFIDAllows the automatic collection of data using RFID tags that contain a chip and an antennaPassive RFID tagsActive RFID tagsPrivacy is a concern53Ensuring Data Quality through Input ValidationThe critical importance of catching errors during input, prior to processing and storage cannot be overemphasizedPotential problemsValidating input transactionsValidating input data54Figure 15.18 Validating input is important to ensure that most potential problems with data are eliminated early55Validating Input TransactionsSubmitting the wrong dataSubmitting of data by an unauthorized personAsking the system to perform an unacceptable function56Validating Input DataTest for missing dataTest for correct field lengthTest for class or compositionTest for range or reasonablenessTest for invalid valuesCross-reference checksTest for comparison with stored dataSetting up self-validating codes (check digit)57Figure 15.19 Steps in converting a five-digit number to a six-digit number containing a check digit58The Process of ValidationCheck first for missing dataCheck the syntaxCheck the semanticsGUI screens can help to reduce the number of human input errors when they incorporate radio buttons, check boxes and drop-down lists59The Process of Validation (Continued)Regular expressionsValidating XML documentsDTDSchema60Figure 15.22 These characters are used in regular expression (pattern) validation61Accuracy Advantages in Ecommerce EnvironmentsCustomers generally key or enter data themselvesData entered by customers are stored for later useData entered at the point of sale are reused throughout the entire order fulfillment processInformation is used as feedback to customers62SummaryQuality of dataEffective codingEffective and efficient data captureValidation of data63Summary (Continued)CodingSequence codesAlphabetic derivation codesClassification codesBlock sequence codesCipher codesSignificant-digit subset codesMnemonic codesUniform character setFunction codes64Summary (Continued)Input devicesKeyboardsOCRMICRMark-sense formsBar codesInput validationInput transactionInput dataEcommerce65