semipersistence

Semipersistence refers to a data structure or algorithm that aims to retain some, but not all, of the benefits of full persistence. In a fully persistent data structure, every previous version of the structure is accessible after an update. Semipersistence relaxes this requirement, often by only making a limited number of recent versions or specific historical states available. This trade-off allows for reduced memory overhead and potentially faster operations compared to full persistence, while still offering the ability to backtrack or inspect past states.

There are various approaches to implementing semipersistence. One common method involves path copying, similar to full persistence, but with a strategy to discard or merge older versions. Another technique might involve maintaining a primary mutable structure and periodically creating a snapshot of it. The specific properties of a semipersistent structure depend heavily on its design and the intended use case. It is particularly useful in scenarios where limited history is sufficient, such as in debugging, undo/redo functionalities in applications, or certain types of transactional systems. The exact definition and implementation can vary, but the core idea is a compromise between the full immutability of persistent structures and the complete mutability of standard ones.