restwhich

Restwhich is a coined term describing a design pattern for RESTful APIs that lets clients specify, within a single request, which resources and fields should be included in the response. The concept combines ideas from sparse fieldsets, resource graphs, and query-like selectors to reduce over-fetch and tailor responses without adopting a full GraphQL interface.

Origin and scope: The term restwhich appears in API design discussions as a shorthand for choosing which data to fetch inside REST. It is not an established standard, but a conceptual pattern used in examples and proposals to illustrate data shaping within RESTful endpoints.

Usage and syntax: A request includes a which parameter that enumerates resources and fields. Example: GET /customers/42?which=profile(name,email),orders(id,total). The server interprets the projection to return only those fields and related sub-resources; nested notation may be supported to shape related data. Some designs use a hierarchical or comma-separated syntax, while others describe field masks or subresource selectors.

Implementation notes: Server-side logic builds a projection from the which clause, mapping to database queries or ORM selections. Caching, versioning, and security considerations apply, and interoperability with existing REST tooling is important. Some implementations overlap with sparse fieldsets or with OData-style query options.

Reception and comparison: Critics argue that restwhich can increase server-side complexity and reduce uniformity across APIs, while proponents see it as a middle ground between rigid REST and GraphQL. It offers a data-shaping mechanism within REST without introducing a new protocol.

See also: REST, GraphQL, JSON:API, OData, sparse fieldsets.