See Wikipedia.[1] Decision tables allow most of the things you really need in a contract. Termination is guaranteed, because there are no loops. Processing is simple; the evaluator goes down the table rows until one evaluates to true. There's a simple tabular way to look at a decision table, so ordinary humans can read them.
Actions should have database-like transactional properties - either everything in the action happens, or none of it does. If you do a send and an update in an action, both must happen, or neither does.
The big question is what primitives you're allowed to call from the table. They'll look a lot like the ones for Solidity, but need to support atomic transactions.
