cerNode>
-addChild(IBindingsProducerNode)
-removeChild(IBindingsProducerNode)
-iterator()

Join Group extends ASTNode implements IBindingsProducerNode
-Optional
-Statement patterns
-Constraints
-Sub groups

Union extends ASTNode implements IBindingsProducerNode
-Sub queries can be groups or statement patterns, but not constraints

Statement Pattern extends ASTNode implements IBindingsProducerNode
-optional: boolean
-scope: Sesame Scope object
-S, P, O, C: TermNode

Constraint extends ASTN