ValueChain with actual path under which it is stored. Used when $(D_PSYMBOL resolve)ing instead of $(D_PSYMBOL get)ing values, allows to inspect not only the value obtained from resolution, but also its origins.
Path tree is a tree where each node has a path assigned. Path is joined with dots which represent tree hierarchy. Each node can hold an optional value. Values are overridable, but history of values is kept, so we can analyze version number for a given node (number of times $(D_PSYMBOL put) was used with that node as target) and revert to previous version of that node as well.
Data structure that wraps the actual value of the node with metadata used for versioning of node values.