I have a Product as shown in the image below. Interactively I am able to constrain the parts as shown. But, when I create the connections using EKL, create constraint works from the Product root.

Example: 

path1 = root->CreatePathString( inst1 , P1)
path2 = root->CreatePathString( inst1 , P2)

createdCoincidence = root->CreateConstraint("MyConstraint"+1 ,"Coincidence" ,path1 , path3 )

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I want to specify Sub Asm Product as the reference.  

path1 = root->CreatePathString( inst1 , P1)
path2 = SubAsm->CreatePathString( inst3 , P2)

createdCoincidence = SubAsm ->CreateConstraint("MyConstraint"+1 ,"Coincidence" ,path1 , path3 )