Object Algebras are a programming technique for the extensible implementation of recursive data types. This extended abstract introduces Object Algebras and shows how they could be used to develop highly evolvable software languages. The paper is concluded with a discussin of directions for further research.
ACM SIGPLAN International Workshop on Formal Techniques for Java-Like Programs, FTfJP 2020, co-located with ECOOP 2020/SPLASH 2020
Software Analysis and Transformation

Inostroza Valdera, P., & van der Storm, T. (2014). Evolving Languages with Object Algebras.