Promotion data type and model

Hi,

I am new to Promote Module of RDF and trying to understand the promotion set up in Promote. Hence few questions:

1. How do we define the data type of Promotion? Guide suggests that this can be either real or boolean.

2. How do we define the model that a promotion has to be a Linear or exponential?

3. What is the difference between Promotion Data type and Promotion Variable Data type? From guide I can understand how promotion variable type is determined, I want to know what difference it makes to the forecasting.

4. Is it a one time activity or promotions can be defined later also and patched to Working RDF?