Verification & Validation F451 AS Computing. Why check data? It’s useless if inaccurate. Also,...
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Transcript of Verification & Validation F451 AS Computing. Why check data? It’s useless if inaccurate. Also,...
Verification & Verification & ValidationValidation
F451 AS ComputingF451 AS ComputingF451 AS ComputingF451 AS Computing
Why check data?Why check data?
It’s useless if inaccurate. Also, wrong data:
Can be annoying
Can cost a fortune
Can be dangerous
£45.67
£297.99X
How do data errors How do data errors happen?happen?
Speeling Mitsakes
Typing the the same thing twice
Leaving an important field blank
Typing wrong numbers – 19/38/05
How can you check data?How can you check data?
Computers use software to check data
2 types of data check:
VALIDATION……Is it valid or Is it valid or
allowed?allowed?
VERIFICATION……Is it the same?Is it the same?
VerificationVerification
Data entered twice, then compared
What common data is verified?
Passwords
ValidationValidation
Ensures data entered complies with allowable data
Many different types of validation include:
Range checksFormat CheckType/Character ChecksPresence ChecksLength CheckLookup/Existence CheckCheck Digits
Class Activity - Are these Class Activity - Are these dates possible?dates possible?
1. 19/12/78
2. 12/19/90
3. 3rd June 1999
4. 30th Feb 2003
5. 31st September 2001
6. 29th Feb 2004
7. 01/01/2003
?
Range check and Type Range check and Type checkcheck
Range checksi.e. is between 1 and 100
Type checksi.e is numeric and not text
Please type in your age:
6000
Please type in your age:
old
Length & Presence Length & Presence checkschecks
Length checkChecks to see if input data contains certain numbers of characters
Presence checkEnsures values have actually been entered in to the data storeCertain key fields are compulsory
Please type in your age:
Please type in your screen name (min 4 characters) JON
Coding dataCoding data
Human data input error is common
Coded values can prevent thisS, M, L can represent small, medium and large
Head Size
Small - SMedium - MLarge - L
F
Look-up CheckLook-up Check
Sometimes, a list box or combo box displays allowable items, so input is selected from a list
Existence CheckExistence Check
Class Exam QuestionClass Exam QuestionSurnameSurname ForenameForename Dept Dept
NumberNumberDept NameDept Name Ext NumberExt Number
Chan Chan D4n D4n 132 132 Accounts Accounts 572 572
Wendy Wendy 123 123 Training Training 467 467
JonesJones Sarah Sarah 121 121 Training Training 468 468
Chan Chan Dan Dan 132 132 Accounts Accounts 572 572
Patel Patel Paul Paul 132 132 Accounts Accounts 573 573 (a) The records in this file have been input with the validation
checking turned off. Referring to the records above, state four problems that have occurred. (4)
(b) Name and describe three different validation checks that would have prevented these problems. (6)
BackupsBackups
Making copy of important files on a portable medium Store the media away from originals If the original file is corrupted it can be replaced quickly
ALWAYS BACKUP YOUR FILES!ALWAYS BACKUP YOUR FILES!
Back-up & Disaster PlanningBack-up & Disaster Planning
Organisations must plan for Organisations must plan for computer failurecomputer failureLarge companies have Large companies have comprehensive planscomprehensive plans
Back up and running within days of Back up and running within days of major catastrophemajor catastrophe
Smaller companies can survive with Smaller companies can survive with less sophisticated systemsless sophisticated systems
Back up system is still vitalBack up system is still vital
The following factors need to be considered when establishing a backup strategybackup strategy:
Back-up & Disaster RecoveryBack-up & Disaster Recovery
• The The frequencyfrequency of backup of backup
• The The mediummedium of storage of storage
• LocationLocation of the media of the media
• Number of Number of generationsgenerations to keep to keep
• The use of The use of full or incrementalfull or incremental backups backups
• Trained Trained staffstaff to implement strategy to implement strategy
• Effective Effective recoveryrecovery procedure. procedure.
• Process should be Process should be documenteddocumented..
Back Up HardwareBack Up Hardware
• Zip DiskZip Disk
• Tape CartridgeTape Cartridge
• DVD-Rom/CD-RomDVD-Rom/CD-Rom
• RAIDRAID
ArchivingArchiving
• Not the same as backupNot the same as backup
• Storing old/unused dataStoring old/unused data
• Taking it from Taking it from server/mainframeserver/mainframe
• Transferring onto storage Transferring onto storage mediummedium
• Stored “off-line”Stored “off-line”
• Unlikely to be used again, but Unlikely to be used again, but still availablestill available
ArchivingArchiving
Storing data files on a portable storage device and keep them in a secure location. Data is stored offline.It can be recovered in an emergency/disaster recovery situation.
Practical ExercisePractical Exercise
Create 3 types of Create 3 types of validation checks validation checks within Delphiwithin Delphi
Range checkRange check
Length checkLength check
Password Password verificationverification
Create 3 types of Create 3 types of validation checks validation checks within Delphiwithin Delphi
Range checkRange check
Length checkLength check
Password Password verificationverification