Type system for declarative data scripting language

A computer system, including:

• at least one computer readable module comprising computer executable instructions representative of declarative code according to a declarative programming model implementing a type system supporting constraint-based type refinement and type membership,
• the at least one computer readable module including a programming construct comprising a refinement type of the type system that defines a type by shaping the type relative to an unlimited top level type representing all types,
• a first expression in the refinement type of the programming construct including a type test construct that tests an evaluation of a second expression that is included in the first expression for membership of an indicated type;
• at least one data store including data with respect to which the at least one computer executable instructions execute to perform at least one of accessing, modifying, filtering, transforming, versioning, or processing of the data based on the programming construct of the declarative code;
• and
• a typechecking module configured to determine whether an error occurs based on at least one judgment that is based on at least one context associated with the at least one type.