Agreements, Promotion rates, Packages, Rate Chains all have a property called 'Level'.
The value set for 'Level' determines which rates can be combined with each other.
The BAR rate (current price for the day) always have level 0.
All offers and rate chains have level 1 by default, this means that they will be applied on the BAR rate but cannot be combined with each other.
If an offer or rate chain have different levels they can be combined.
For example:
An Agreement have level 1.
A promotion rate have level 1.
Rate chain "long stay" has level 2.
Rate chain "early bird" has level 3.
The agreement and the promotion rate cannot be added to the same room reservation.
The two rate chains can be applied on top of the agreement and on top of the the promotion rate if the conditions of the rate chains are fullfilled.
The rate chains will also be applied on any reservation if the conditions are fullfilled, either one of the rate chains or both can be added depeding on the conditions.