Revenue Recognition" Please responds to the following:

In some situations, revenue is recognized as it is earned in the economic sense. In other situations, a criterion such as the point of sale is used to recognize income. Validate why revenue is often recognized as earned at the time of sale. 

Create a situation or scenario in which it may be appropriate to recognize revenue as the productive activity takes place. State whether or not there are any other times appropriate for recognizing revenue. Provide a rationale with your response.