1:1 Self Relationship is hard to model. Need advice.

Question

Here is a quick example of the problem using boats...
Create an entity "the boat".
Create a 1:1 relationship of "the boat" to "the boat". Call both the forward and reverse text "the other boat"
Here is the original text from the rules document: When boats are on opposite tacks, a port-tack boat shall keep clear of a starboard-tack boat.
Here is the modeled rule:
the boat is required to keep clear if
     the boat is on a port tack and
     for(the other boat, the boat is on a starboard tack)
When you debug this and create 2 boats, you will see that each boat actually has 2 relationships. The rule doesn't actually work intuitively. Both relationships must be set.
How do people solve this problem?

Answer 1

From your description, I think what you're after is cross entity reasoning.
As a start, have a look at the Entity and Relationship Functions, particularly the example rule about twins (search for the word "twin" on the page): http://download.oracle.com/docs/html/E24270_01/Content/Reference/Rule%20syntax%20reference/Entity_and_relationship_functions.htm
In the twin example, there are multiple instances of 'the child', and for each instance of 'the child' the rule works out whether or not it is a twin by comparing one child's date of birth with another child's date of birth. Obviously this isn't exactly the logic you're after, but you should get some ideas to explore if you look into the cross entity reasoning functionality and inferred relationships logic.
Cheers,
Jasmine