Coding Data - ASAL Information Technology 9626 Notes on Chapter 1 & 6 along with additional PDF

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IT (9626) Theory Notes  

CodingData Whatiscodingofdata? Anysystemwillneedtohavedatacollected,enteredandstored.Onemethodofstoringdatais toassigncodestoit.Thisusuallymeansshorteningtheoriginaldatainanagreedmanner. Example1

Originaldata:Monday;Tuesday;Wednesday;Thursday;Friday Codeddata:Mon;Tues;Wed;Thurs;Fri Example2

Originaldata:XtraLarge;Large;Medium;Small Codeddata:XL;L;M;S

Reasonstocodedata: Itiscommonformuchofthedatacollectedandenteredintoasystemtohavesomedegreeof repetitionandredundancyi.e.extrainformationthatdoesnotaddanything.Andthispatternor repetitioniswhyitisefficienttocodethedatainsomeway. 

Speedingupdataentry

Let'staketheexampleofcollectingdataaboutaperson'sgender.Peoplecanbeeither 'Male'or'Female'. Whilstthesetwooptionsareeasilyunderstoodbyall,imaginehavingtoentertheword 'Male'and'Female'intoasystemmanyhundredsoftimes.Itisawasteoftimeandeffort becausenoextrainformationiscontainedinthefullwordscomparedtoasingleletter. 

Increaseaccuracyofdataentry

Theotherissueisthatnomatterhowaccurateapersonisatdataentry,atsomestage theyarelikelytomakeamistakeandmightspell'Male'as'Mail'or'Female'as'Femal'. Thistypeofmistakewillmakeanyresultsfromyourdatabasequeriesunreliable. Insteadofentering'Male'or'Female'youcouldcodethedataandinsteadenteritas'M' or'F'. Simplyhavingtoenteroneletterinsteadofapossiblesixwillspeedupdataentry.Itwill alsocutdownontheriskofmistakesbeingmadewithspelling. 

IT (9626) Theory Notes 

 

Useofvalidation

Whendatahasbeencodeditmakesiteasiertousevalidationtocheckifthedata enteredissensible.Withtheexampleabove,thepersonenteringthedatacouldstill makeamistakeandenter'S'insteadof'M'or'F'. Butifyousetupvalidationsothatthefieldwillonlyaccepttheletters'M'or'F'and absolutelynothingelsethenthatshouldfurthercutdownonpossiblemistakes. 

Lessstoragespacerequired

Everyletterthatyoustoreinyourdatabasesystemwilltakeatleastonebyteofstorage. Ifyoustore'Female'as'F'thenyouwillsavefivebytesofstoragespace.Ifthesystem belongstoalargeorganization,theremightbemanythousandsormillionsofrecords stored‐simplybycodingonefield,ahugeamountofharddiskstoragecanbesaved. 

Fastersearchingfordata

Thesmallerthesizeofyourdatabase,thefasteritwillbetosearchandproduceresults. Thusbycodingdataandkeepingthesizeofthesystemtoaminimumthemoretimeyou cansaveinthelongrunwhenrunningqueries.

Problemscausedbycodingdata: Whilstcodingdatacanbringmanybenefitsitcanalsoleadtosomeproblems. 

Coarseningofdata

Thismeansthatduringthecodingprocesssomeofthesubtledetailsinthedataarelost. Thecolourscouldbeclassedas: Lightpink,paleblue,blackandmidblue However,whenthesecoloursarecodedtheymaybecome: PK(pink),B(blue),BK(black),BE(blue) Inthiscase,noallowancehasbeenmadeforshadesofcolours.Thefinedetailhasbeen lost.Thisiswhatismeantby'coarseningofdata'. 

Codingcanobscurethemeaningofthedata

Areaderseeingthe'gender'dataasM/FisprettylikelytoknowthatitmeansMale/ Female. 

IT (9626) Theory Notes 

 Butsomecodesaremoreobscure,forexamplethecountrycodeforSwitzerlandisCHE. Manypeoplemightnotrecognizewhatthiscoderepresents. 

CodingofValueJudgments

Whenyouarecollectingdataaboutpeople'sopinionsitmightbedifficulttocodetheir answerswithaccuracy.Thecodetheygivewilldependontheirindividualopinion.Coding ofvaluejudgmentswillinevitablyleadtocoarseningofthedatasincetherewillbeawide rangeofopinionsthatcouldbeheldandonlyalimitednumberofcodesavailable.

Furtherexamplesofdatacoding: Inoureverydayliveswecomeacrossmanyexamplesofhowcodingisusedtorepresentdata. Herearejustafewmoreideas: 

Countrynames

Thenameofacountrycanberepresentedbytwoletters.Forexample: GreatBritain‐GB France‐FR Canada–CA 

Airlineflightcodes

Whenyouflyyoumayhavenoticedthatyourflightisgivenacode. Thiscodeconsistsoftwoletterstoidentifytheairlinethatyouareflyingwith.Theletters areusuallyfollowedbynumberstorepresentaparticularroute. Examples: Soforexample,aBritishAirwaysflightfromHeathrowtoOslomightbecodedasBA766. AflightoperatedbytheairlinecompanyEmirateswhichdepartfromDubaiandarrivesat HeathrowmightbecodedasEK029.

Advantagesofcoding: ‐Dataentrycanbefaster ‐Dataentrycanbemoreaccurate ‐Validationcanfurtherimproveaccuracy ‐Lessstoragespacerequired

IT (9626) Theory Notes 

 ‐Fastersearchingfordata ‐Codeddatacanbemoresecureifpeopledon’tknowwhatitmeans

Disadvantagesofcoding: ‐Coarseningofdata ‐Meaningofdatacanbeobscured ‐Valuejudgmentsaredifficulttocode ‐Ifpeopledon’tknowthecodeitcanslowdowndataentry ‐Ifcodesarecomplicatedtheymightbeenteredincorrectly ‐Mightrunoutofcodecombinations

IT (9626) Theory Notes  

DataEncryption WhatisEncryption? Encryptionmeanstoscrambledatainsuchawaythatonlysomeonewiththesecretcodeorkey canreadit.

Whyisitimportant? Today,encryptionisfarmoresophisticated,butitservesthesamepurpose‐topassasecret messagefromoneplacetoanotherwithoutanyoneelsebeingabletoreadit. Encryptionisextremelyimportantfore‐commerceasitallowsconfidentialinformationsuchas yourcreditcarddetailstobesentsafelytotheonlineshopyouarevisiting. Webbrowsersareabletoencryptyourpurchasedetailsusinganencryptionmethodcalled'SSL' (SecureSocketLayer).Youknowthisisswitchedonwhenasmallpadlockappearsinthebottom rightofthebrowser.SSLgetsswitchedonwhenyouvisita'secureserver'thathasanaddress thatstartswithHTTPS://(notethe'S').

Howdoesitwork? Encryptionworksbyscramblingtheoriginalmessagewithaverylargedigitalnumber(key).This isdoneusingadvancedmathematics.Commercial‐levelencryptionuses128bitkeythatisvery, veryhardtocrack.Thecomputerreceivingthemessageknowsthedigitalkeyandsoisableto workouttheoriginalmessage.

Problemswithencryption Therearethreeproblems; a)Itisslowerthannormalbrowsing.Ittakesawhileforthebrowsertodothemathsrequiredto scramblethemessageandanotherdelayontheserverthathastounscramblethedata. b)Onlineshopshavetohaveadigitalcertificatethatcontainspartofthekey.Thisisnotfree andhastobesuppliedbya'certificateauthority'. c)Itcanbeacomplicatedbusinessrunningasecureserver,soveryoften,ordinaryonlineshops willhireaspecialist'PaymentGateway'suchasWorldPayorPaypaltohandlepaymentsfor them.

 

IT (9626) Theory Notes 

 SymmetricvsAsymmetricencryption SymmetricEncryption Symmetricencryption’sjobistotakereadabledata,scrambleittomakeitunreadable (protectingitfrompryingeyeswhileit’sbeingstoredonadiskortransmittedoveranetwork), thenunscrambleitagainwhenit’sneeded.It’sgenerallyfast,andtherearelotsofgood encryptionmethodstochoosefrom.Themostimportantthingtorememberaboutsymmetric encryptionisthatbothsides—theencrypter,andthedecrypter—needaccesstothesamekey. AsymmetricEncryption Asymmetricencryptionalsotakesreadabledata,scramblesit,andunscramblesitagainatthe otherend,butadifferentkeyisusedforeachend.Encryptersuseapublickeytoscramblethe data,anddecryptersusethematchingprivate(secret)keyontheotherendtounscrambleit again. Thepublickeymeansthatitcanandshouldbepublished.(Thisiswhyasymmetricencryptionis alsooftenreferredtoaspublic‐keyencryption),buttheprivatekeymustbekeptprivate, protectedmuchlikethekeyforsymmetricencryption. 

IT (9626) Theory Notes  

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 Data,InformationandKnowledge Data Dataiscomprisedofthe basic,unrefined,and generallyunfiltered information

 

Information Information…ismuchmore refineddata…thathasevolved tothepointofbeingusefulfor someformofanalysis



Knowledge Knowledgeresidesinthe user…happensonlywhen humanexperienceandinsight isappliedtodataand information

 

Dataisunprocessedfactsandfigureswithoutanyaddedinterpretationoranalysis."Thepriceof crudeoilis$80perbarrel."



Informationisdatathathasbeeninterpretedsothatithasmeaningfortheuser."Thepriceofcrude oilhasrisenfrom$70to$80perbarrel"givesmeaningtothedataandsoissaidtobeinformation tosomeonewhotracksoilprices.



Knowledgeisacombinationofinformation,experienceandinsightthatmaybenefittheindividual ortheorganization."Whencrudeoilpricesgoupby$10perbarrel,it'slikelythatpetrolpriceswill riseby2pperliter"isknowledge.

IT (9626) Theory Notes  

DataValidationandVerification Validation: Validationisonewayoftryingtoreducethenumberoferrorsinthedatabeingenteredinto yoursystem.Validationisperformedbythecomputeratthepointwhenyouenterdata.Itisthe processofcheckingthedataagainstthesetofvalidationrules. Validationaimstomakesurethatdataissensible,reasonable,completeandwithinacceptable boundaries. Datavalidationcanbeperformedbyusinganumberofvalidationchecks. RangeCheck Arangecheckiscommonlyusedwhenyouareworkingwithdatawhichconsistsofnumbers, currencyordates/times. Arangecheckallowsyoutosetsuitableboundaries: 

Boundary

Description

Validation

Upperlimit

Themaximumpriceofanyiteminashopis £100

=0

Arange

toachieveaBgradeyoumustscorebetween 75%‐84%

>=75AND...