In this blog post, the author introduces Small-Step Operational Semantics (SOS) and demonstrates its use in designing a tiny programming language called SagaLang for developing sagas. Sagas are long-running transactions that guarantee either exactly once or not at all execution. The author presents three iterations of SagaLang, each with different failure mitigation strategies: basic execution model, sagas with forward recovery, and sagas with backward recovery. While the language is minimalistic, it effectively illustrates the ideas behind SOS and its role in providing precise specifications for programming languages and systems.