+// binStatistic x
+// conditionalStyle x y
+// graphLayoutStatistic labeling
+// color shape x y
+// color*2 size shape x y
+// color size shape color x y
+// labeling styleBy x y
+
+graphLayoutStatistic
+ :from=ref (sourceVariable | derivedVariable | expressionVariable)
+ :to=ref (sourceVariable | derivedVariable | expressionVariable)
+ :nodes=ref (sourceVariable | derivedVariable | expressionVariable)
+=> initial (move | swap)?
+
+shape
+ :cycle=ref styleCycle
+ :variable=ref (sourceVariable | derivedVariable | expressionVariable)
+ :clamp=bool?
+ :domain=ref categoricalDomain?
+=> symbolMapping*
+
+symbolMapping
+ :from
+ :to
+=> EMPTY
+
+image
+ :variable=ref (sourceVariable | derivedVariable | expressionVariable)
+=> stringMapping+
+
+stringMapping
+ :from
+ :to
+=> EMPTY
+
+initial
+ :type=(grid | circle | data)
+=> EMPTY
+
+move => EMPTY
+
+swap => EMPTY