Version Trees

With full persistence, versions form a tree (or DAG with confluence):

class VersionedStructure:
    roots: map from version_id to root
    parent: map from version_id to parent_version_id

    function update(version, ...)
        newRoot := ...
        newVersion := nextId()
        roots[newVersion] := newRoot
        parent[newVersion] := version
        return newVersion

    function getAncestors(version)
        result := []
        while version is not null
            result.append(version)
            version := parent[version]
        return result

You can traverse the version tree for debugging or analysis.