Requirements of error handling

What is a good error-handling system? Besides aesthetic considerations, a good error-handling system is generally held to meet the following requirements:

• It is triggered without failure in case of any kind of error in the system.
• It allows the application to automatically take the appropriate actions.
• The error message displayed to the user gives a clear description of what is wrong and what action must be taken to proceed.
• If assistance is required, the error message helps the user to interact with the help desk and gives the help-desk team the necessary information to react easily and quickly.
• The logged information gives the development team the necessary information to identify the error, locate its source point in the application code, and fix the issue.
• The error-handling code should not degrade code readability. While essential, error handling is only a safety net, and therefore of less priority than the application's primary functions.