Users may prefer to use semantic complements like in Discourse Graph (supports and supported by)

This could be done by creating a special reserved relationship called complements, and allowing a user to create a complement as follows

- [[supports]]
	- [[complements]] ->
    	- [[supported by]]

and now the plugin can treat the following two aspects as equivalent

- [[some evidence]]
	- [[supports]] ->
    	- [[a claim]]
- [[a claim]]
	- [[supported by]] ->
    	- [[some evidence]]