New: first signs of life of an Event context
Think of a (Unix) file system. A top directory, then data files or more directories, of virtually unlimited depth. They have two important properties:
1) Unix directories are “Composite Objects” ( a directory can contain files, other directories, which in turn can contain…)
2) Each file/directory has a name.
We map that on a node structure: We define (in C++) Nodes and CompositeNodes (they can contain other Nodes and in turn CompositeNodes).
Each node which is not composite (a directory, that is) can contain an arbitrary other (user-defined) object in “its belly”. These user object are the payload, the nodes just the containers to store them.
In this way we define a tree structure which is being build up in the analysis process.
Analysis modules typically add named entries at a certain point in the tree hierarchy (they don’t normally delete entries).