So from what I've gathered from the stickies and random threads a scenegraph is a hierarchical tree based structure designed to represent entities in a parent-child relationship.

Fine and dandy but what I'm more interested in is what data belongs in the scenegraph and how should it be attached to the nodes.

For the most part people agree that nodes shouldn't have a "render" function so should nodes still be able to have rendering data attached to them such as shaders, vertices, and bounding primitives. If that data should still be there I'd assume it wouldn't be in the node definition but rather attached to the node and held in some other data structure.

Should it contain spatial information like matrices? Is this all dependent on the specific situation, because honestly it would seem that there are a few thing such as matrices that could fit into the node definition that would work in all games, regardless of the type or genre or engine.

Also a node and leaf would be their own class/structure so I'd also assume that they don't represent game entities specifically and nodes may have entities attached to represent data specific to the engine?