Is there a "Grammar of Data Schemas/Constraints" similar to "Grammar of Graphics"? Any schema definition language you find interesting?

An interesting question. The grammar of graphics sums up how to present data for good reception by the human visual system. A grammar of data schemas would address which external constraints? There's the "human-readable" constraint, which led to JSON, YAML, TOML, etc. Schemas live in a layer on top of those formats. So what would be useful constraints in that layer?