Subsume means1/1/2023 ![]() ![]() The Concise Data Definition Language (CDDL) is used to defineĬDDL shares many of the same constructs from CUE, includingĭisjunctions, embedding, optional fields, and definitions.ĬDDL, however, has no value lattice and does not define mathematical Unlike Rego which will be more reminiscent of a Datalog program.īut more importantly, CUE’s approach is more amenable to finding normalizedĪnd simplified representations of constraints, which makes it more suitable Using a Datalog variant for what is essentially a constraintĭatalog makes an excellent query language.īut for constraint enforcement, it is a bit cumbersome as one effectivelyįirst needs to query values to which to apply the constraints.ĬUE collates the constraints with the location of the data to which they apply.Īs a result, CUE constraints look a lot like the data they constrain, Of Prolog for applications in encoding human languages. Typed-feature structures were designed to deal with the shortcomings Typed-feature structure or graph unification. It is based on Datalog, a restricted form of Prolog, whereas CUE is based on Rego, like CUE, has its roots in logic programming. Used for Open Policy Agent (OPA), also solves the issue of being able to Note that CUE is generally more expressive and many CUE constraints willĪlthough not designed as a data definition language, Rego, the language The JSON format of OpenAPI makes it good interchange standard.ĬUE, on the other hand, can serve as an engine to generate and interpret The difference gets more extreme as more constraints and logical Compile ( "apis", /* text of the above API */ ) if err != nil If the old one is an instance of the new one. In CUE, an API is backwards compatible if it subsumes the older one, or Only use fields that are explicitly defined. - You can now specify your age and your hobby!ĭeclarations with a name starting with # are definitions.ĭefinitions are not emitted when converting to data, for instance whenĮxporting to JSON, and thus do not need to be concrete in such cases.ĭefinitions assume the definition of closed structs, which means a user may Core issues addressed by CUE Validating backwards compatibilityĬUE’s model makes it easy to verify that newer versions of schemaĪre backwards-compatible with older versions.Ĭonsider the following versions of the same API: // Release notes: ![]() This limits these standards in various ways. OpenAPI even allows for complex logical combinators.Ī key difference, however, is that these standards do not unify schemaĪnd values-the thing that makes CUE so powerful. Values, ranges, and various other constraints. Standards like OpenAPI and CDDL allow defining things like default More than just describing whether a field is an integer or a string. Most modern dedicated data definition languages or standards allow To verify implementations, validate inputs, or generate code. The structure defined by such a language can, in turn, be used Defining schema to communicate an API or standard.Ī data definition language describes the structure of data. ![]()
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