Abstract: This application relates to calculating addresses of modifications to tree-based structures and storing some of the addresses in a manner that allows the modifications to be applied, sustained, modified, and removed independently from one another. In some embodiments, the tree-based structures may define documents, including web documents, and the modifications may include annotations. In some embodiments, the addresses may include locations of the annotations within the documents. Methods and systems disclosed herein also include improved methods and systems for handling annotations. Some such methods and systems operate in connection with handling addresses associated with tree-based structures, while others can function independently of tree-based structures. Related user interfaces, applications, and computer program products are disclosed.