Software Engineering basics - Validity check &Consistency check

1. Validity Check

Definition:
A validity check ensures that the data entered is correct and acceptable according to predefined rules, formats, or constraints.

Purpose:

  • To ensure that input values are sensible and within allowed limits.

  • Prevents incorrect or invalid data from being accepted by the system.

Examples:

  • A date field should be in the format DD/MM/YYYY.

  • Age should be a number between 0 and 120.

  • Email addresses must contain @ and a domain.

Key Point:

  • Validity checks focus on individual data items.

2. Consistency Check

Definition:
A consistency check ensures that related pieces of data do not conflict with each other.

Purpose:

  • To maintain logical integrity and coherence among data items.

  • Detects contradictions or mismatches between related data.

Examples:

  • Start date of a project should not be after the end date.

  • Total of individual line items should equal the invoice total.

  • If a user is marked as "married," marital status details must be present.

Key Point:

  • Consistency checks focus on relationships between multiple data items.

3. Key Differences Table

Feature Validity Check Consistency Check
Purpose Ensures data is correct and acceptable Ensures data is logically coherent with other data
Focus Single data item Multiple related data items
Example Age is between 0-120 Start date ≤ End date
When Used During data entry During data processing or validation of related fields

Summary

Validity check = Is the data acceptable?
Consistency check = Does the data make sense together?