anchor.diff:    For exampe, `{a: 1} \<= {a: 1, b: null}` evaluates to `null`.
     ** Regular maps are <<incomparable>> to any value that is not also a regular map.
     * Nodes
  -  ** The comparison order for nodes is unspecified and left to implementations.
  +  ** The comparison order for nodes is unspecified here and left to implementations.
  +  However implementations are required to define a fixed comparison oder between nodes.
     ** Nodes are <<incomparable>> to any value that is not also a node.
     * Relationships
     ** The comparison order for relationships is unspecified and left to implementations.
  +  However implementations are required to define a fixed comparison oder between relationships.
     ** Relationships are <<incomparable>> to any value that is not also a relationship.
   - Paths
     ** Paths are compared as if they were a list of alternating nodes and relationships of the path from the start node to the end node.
  
positive.code: 
  `expr1 = expr2` if and only if `expr1 >= expr2 && expr1 \<= expr2`.
  
  Comparability and equality use <<unknown-null,"unknown" `null` values>>.
  
  [[incomparable,incomparable]]
  ==== Incomparability
  
negative.code: - Implementation-specific types
    * Implementations may choose to define suitable comparability rules for values of additional, non-canonical types.
    * Values of an additional, non-canonical type are expected to be <<incomparable>> to values of a canonical type.
  - `null` is <<incomparable>> with any other value (including other `null` values).
  
  [[equality-def,equality]]
  ==== Equality ====
  