Generally when it comes to appraisal it is always done in the end of the year so we may not have all the updates that a person has contributed good / bad for the whole year.
when we are in the team management, it is better to review the appraisal document for each person in a smaller frequency ie)monthly once or on alternate months,
this methodology will give us to document the way the person has performed during each month, the contributions that helped to resolve issues or the areas that person has to improve.
as we monitor this monthly / alternate month it will be good to communicate to the individual for their accomplishments and also the areas that they have to still perform.
In projectized environment the resources may not be associated with one project manager throughout the year, so when some other request some feedback for the appraisal about the resource who have partially worked or contributed such kind of documentation will help us better.
Also during the appraisal discussions both the appraiser and appraiser will have enough information to talk and will help the resource to identify the strength and weakness.