OData

OData (Open Data Protocol) is a standard, approved by OASIS and later ISO/IEC, for building and consuming queryable RESTful APIs. Where plain REST leaves every provider to invent its own conventions, OData prescribes a shared query language, a metadata format that describes the data model, and consistent response shapes. Originating at Microsoft, it is widely used across enterprise systems, particularly in the Microsoft and SAP ecosystems.

• Uniform query syntax - A URL-based grammar ($filter, $select, $expand, $orderby, and more) lets clients query any OData service the same way.
• Machine-readable metadata - A $metadata document exposes the entity model so tools and clients can discover types and relationships without human documentation.
• Entity data model (EDM) - A formal way to describe entities, properties, and their relationships that underpins the whole protocol.
• REST conventions - Standardizes CRUD, paging, and error handling so behavior is predictable across providers.

In real API operations OData is a trade-off between consistency and flexibility. Its self-describing metadata and uniform query language make it excellent for exposing rich enterprise data stores where clients need ad-hoc querying without a bespoke endpoint for every access pattern — which is exactly why SAP, Microsoft Dynamics, and Business Central lean on it heavily. The cost is that it is heavier and more opinionated than a hand-designed REST API, and its query surface can be hard to govern and secure. It sits alongside GraphQL as one of the standardized answers to “let the client shape the query,” and like any queryable interface it benefits from a clear contract that tools can read.