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Quality: What Is “Reliability” About?

·271 words·2 mins

When am I reliable?

Well, there may be different criteria for people. For your software it is about the required functions working under the required conditions. Usually there is also a time span required for this.

You see, once again it’s about meeting requirements.

The ISO 25010 quality model divides reliability into:

Maturity #

How well does your software meet the requirements in normal operation?

Check here:

  • What are the expectations?
  • What occurs in everyday operation?
  • Where are there difficulties?

Example: Your logistics system can process delivery information without a mobile network.

Availability #

How ready and accessible is your software when it is needed?

Here you check:

  • When does your software need to be up and running?
  • Does your software respond as required?
  • What keeps users from being able to use your software?

Example: Your hospital information system responds within 5 seconds to input at the admission terminal for every emergency admitted.

Fault tolerance #

Does your software work as intended despite hardware and software failures?

Check for this:

  • Does your software work even if the described hardware is not present?
  • Does your software still work when the given software has failed?
  • In which situations does your software stop working?

Example: Your system works without limitations when the wired network and the barcode scanner are down.

Recoverability #

How quickly/easily is your software back to the desired state after a failure?


  • What data/what state needs to be restored?
  • Is this state saved?
  • How long does it take to restore the data/state?

Example: All status information is persisted in the database. Restoring this database takes a maximum of 3 minutes.