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