Today we continue our discussion on how to deal with rule versioning and rule history in a declarative way. In our first column[1] on this topic we described the characteristics of the rule history and versioning problem, and we discussed an example and a simple solution. In our second column[2] on this topic we discussed an efficient and declarative solution that can be used when rules are versioned on a small number of dates (for example every year on the first of January).

This column is the first in a series that will provide the reader with best practices on using or choosing a rules engine. The following topics will be discussed in future columns:

* magic values
* rule templates
* rule on/off
* exception handling
* what to do procedural, when to do rules
* local variables in rules
* arrays and chaining
* forward chaining over multiple instances
* backward or forward chaining?