1. A method of determining node similarity for component substitution, the method carried out by program code stored on non-transient computer-readable medium and executed by a processor, the method comprising: determining similarity metric values between nodes of a target system tree associated with a target system and nodes in other system trees respectively associated with other systems, wherein each system comprises components and nodes of each system tree represent respective ones of the components of the associated system, wherein the determining comprises comparing nodes of the target system tree with respective nodes of the other system trees by applying at least one of domain based rules and attribute based similarity metrics to attributes of the system components represented by the nodes being compared, and assigning a similarity score to each node of the other system trees compared to a respective one of the nodes of the target system tree based on results of the comparing; and for at least one of the nodes of the target system, identifying replacement ones of the nodes of the other system trees based on their respective assigned similarity scores.