# A strengthening of the MCFL-ness of O2

arXiv: https://arxiv.org/abs/2608.18813 · HTML: https://mlsanity.com/paper/2608.18813/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 2 of its 13 references that are in the map.
- First posted on arXiv 19 Aug 2026.

## Builds on (most cited first, 2 of 2)

- [A short proof that O2 is an MCFL](https://mlsanity.com/paper/1603.03610/) (2016)
- [O2 is a multiple context-free grammar: an implementation-, formalisation-friendly proof](https://mlsanity.com/paper/2405.09396/) (2024)

## Abstract (arXiv)

In the last years, a number of proofs of the fact that O2 is a multiple context-free grammar (MCFG) were given. Such results can be exploited in the fields of both computational linguistics and of computational algebra. Here, we focus on a recent such proof spelled in terms of factorizations of string tuples, and give a new result with a stronger characterization of such factorizations than in existing theorems.