What is a therom?

Answer 1

Techniques used for validation and verification

Data entered into a database or spreadsheet is usually checked using processes called validation and verification.

Validation is an automatic computer check to ensure that the data entered is sensible, reasonable, complete and within acceptable boundaries. It does not check the accuracy of data. The checking of the data entered is done by software that can either be part of the input system or a separate program that checks the data.

Types of validation

There are a number of validation types that can be used to check the data that is being entered.

· Range check: checks that a value falls within the specified range, it will reject any data items outside an expected range. For example, number of hours worked must be less than 50 and more than 0.

· Presence check: checks that data has been entered into a field, it will reject the data where the required fields have been left blank. For example, in most databases a key field cannot be left blank.

· Length check: ensures that the data entered is of reasonable length. For example, a password which needs to be six letters long.

· Type check: ensures data is of a particular data type. For example, a number of items in stock will be entered as an integer (whole number).

· Format check: ensures a data item matches a pre-determined pattern of letters and/or numbers. For example, a National Insurance number is in the form LL 99 99 99 L where L is any letter and 9 is any number

· Lookup checks: ensures that data matches one of a limited number of valid entries. For example subjects studied in a school should be selected from a list of Mathematics, English etc.

Verification is a process used to check that the data has been entered accurately, is consistent and has not been corrupted. Verification confirms the integrity of data as it is copied between different parts of a computer system. Copying should not change the data. Differences detected would mean an error in the transfer.

Types of verification

The verification checks may include:-

· Double entry verification: to ensure data typed into a computer system is entered accurately. The data is entered twice, by different operators, and compared by the system. Any differences can be identified and manually corrected.

· Visual verification: data is entered and the original data is compared to the data entered into the system; for example by comparing the data on the data on the data capture form with a printout of the database, or with the entered data on the screen.