Odata

OData stands for Open Data Protocol, a web protocol for querying and updating data. It defines a standard way to expose data via RESTful services, enabling clients to discover and manipulate data sets using uniform URLs and query options.

OData is based on HTTP, REST principles, and commonly uses JSON or Atom/XML for data payloads. It models data with the Entity Data Model (EDM), including entities, complex types, relationships, and entity sets. A service exposes metadata at the $metadata endpoint, describing the model and available operations. Clients navigate resources with URIs and can use query options such as $filter, $select, $expand, $orderby, $top, and $skip to shape results. The protocol supports create, read, update, and delete (CRUD) operations, batch requests via $batch, and concurrency control through ETags.

Actions and functions extend the model with server-side logic. OData supports navigation properties to traverse relationships, and provides support for paging, counting, and server-side paging. Data formats include JSON (often OData JSON) and Atom/XML, with JSON increasingly preferred for modern clients. Security relies on standard HTTP authentication schemes and can be integrated with OAuth, OAuth2, and other schemes.

OData originated at Microsoft and was formalized as an open standard by OASIS, with ongoing development leading to OData v4. It has wide adoption across platforms and languages, with implementations in Microsoft, SAP, and various cloud services, enabling interoperable data APIs and data services.