This is a nice conversation ;)
Modify Search is slightly misunderstood.
It is a specialized case different from normal search because , Modify search is available only after search results are displayed through regular search.
My fault.I should have been more clear.
So, once results are generated through regular search, User can modify the search criteria.
Consider this example:
User is searching for Condo in an area nearby.
In regular search (hypothetical), User specifies Zip Code and mmm...let's say his/her budget.
Now, search results are displayed.
Below, there is Modify search widget. The Modify search widget is a set of radio buttons. Each Radio button relates to a price range.
Hence, the User can now change his/her price range but not Zip Code. The Zip Code is still what was entered for regular search.
IMHO, this is a good case for "Extends" dependency.
And for "send results via Email" and "print" actions are optional. user who performs a search does not have to compulsorily send results or print them.
Whereas, "Includes" relationship requires that the action be performed "at least once" which means, the send results and Print actions would be compulsory.
That's what i know or i think i know
Sorry for the ambiguity in my previous posting.