+## Scene Graph {#scene-graph}
+
+From Wikipedia...
+
+A scene graph is a collection of nodes in a graph or tree structure.
+A node may have many children but often only a single parent,
+with the effect of a parent applied to all its child nodes;
+an operation performed on a group automatically propagates
+its effect to all of its members. In many programs, associating
+a geometrical transformation matrix (see also transformation and matrix)
+at each group level and concatenating such matrices together is an
+efficient and natural way to process such operations. A common feature,
+for instance, is the ability to group related shapes/objects into a
+compound object that can then be moved, transformed, selected,
+etc. as easily as a single object.
+
+### How does this relate to the DALi public API?
+
+Actors are effectively nodes that receive input (touch events) and act as a
+container for draw-able elements (which are also nodes) and other actors.