ZetaSQL defines a language (grammar, types, data model, and semantics) as well as a parser and analyzer. It is not itself a database or query engine. Instead it is intended to be used by multiple engines wanting to provide consistent behavior for all semantic analysis, name resolution, type checking, implicit casting, etc. Specific query engines may not implement all features in the ZetaSQL language and may give errors if specific features are not supported. For example, engine A may not support any updates and engine B may not support analytic functions. Until all this code is released, we cannot provide any guarantees of API stability and cannot accept contributions. We will also be releasing more documentation over time, particular related to developing engines with this framework. Documentation on the language itself is fairly complete.