Again i say to this question can't be answered properly until,
We know around 5 things.

What type of ratings are we dealing with 1st.

1-Weight ratings.
2-Class ratings.
3- Speed ratings.
4- Statistical ratings.
5 Paid for ratings (Bet Selector)(Cyber horse virtual form guide)etc,
That use all, or a combination of the above.

Once we know what type of ratings the Author refers to,
We can start to list certain elements.

Cheers.