Visitor design patterns decouples the data structure and the algorithms. Traversal could be in-order or post-order. Applications include sorting such as binary sort in O(log n) complexity. The tree and maze illustrate a dichotomy in software and systems infrastructure. They are essential ingredients in an ecosystem. Use cases include the rationalization of taxonomies/thesauri and cognitive biases. Eg. man-woman, snakes-ladders, import-export, left-right, train-test.