Hello,

If you are looking to set product rating system, you can use Rating control which is also used in a sample E-commerce site. It would be probably best to use it in a transformation similarly to the following (this is an example from Datalist web part's transformation for products):

<cms:RatingControl ID="elemRating" runat="server" Enabled="false" RatingType="Stars" ExternalValue='<%# EvalDouble("DocumentRatingValue")/(EvalDouble("DocumentRatings") == 0?1:EvalDouble("DocumentRatings")) %>' />

Best regards,
Filip Ligac