anchor.diff:  * Which should be more reasonable, NULL eq NULL is true or false ?
     ** If it is true, it may be respected in JOIN operation
   * There are a number of situations where the Gremlin grammar won’t support some of the examples - to what extent do these sorts of constructs need to exist in the grammar? Not having them would impact the ability to supply tests that enforce the behaviors that we’ve outlined. 
  -* Should UUID be a different type to be taken into account ?
   
   == Technical Appendix
   
  
positive.code: ===== String
  * String value is ordered lexicographically
  
  ===== Date
  * Date value is ordered chronologically
  
  
negative.code: * BigInteger
  * BigDecimal
  * String / Char
  * UUID
  * Date
  
  Note that in Double or Float, we have a concept of INFINITY / https://en.wikipedia.org/wiki/Signed_zero[signed-zero], and NaN.
  