In information technology, gap analysis is an important assessment tool which helps to identify differences between information systems or applications. A gap is sometimes called "the space between where we are and where we want to be."
A gap analysis helps bridge that space by highlighting which requirements are being met and which are not. The tool provides a foundation for measuring the investment of time, money and human resources that's required to achieve a particular outcome.
In software development, for instance, a gap analysis can be used to document which services and/or functions have been accidentally left out, which ones have been deliberately eliminated and which still need to be developed. In compliance, a gap analysis can be used to compare what is required by law to what is currently being done.
Service performances can be also valued with the help of effective cyclic gap analysis process. Lessons learned over this cycle is the foundation stone for laying down the success definition of an IT Service.
A common policy which I always follow through is : Why to trust the instincts when I can verify the complete data...