OData, short for Open Data Protocol, defines a protocol for the querying and updating of data utilizing existing Web protocols. OData is a REST-based protocol for querying and updating data and is built on standardized technologies such as HTTP, Atom/XML, and JSON. It is different from other REST-based web services in that it provides a uniform way to describe both the data and the data model.
It is considered to be a flexible technology for enabling interoperability between disparate data sources, applications, services and clients.
In May, 2012, companies including Citrix, IBM, Microsoft, Progress Software, SAP AG, and WSO2 submitted a proposal to OASIS to begin the formal standardization process for OData. Many Microsoft products and services support OData, including Microsoft SharePoint, Microsoft SQL Server Reporting Services, and Microsoft Dynamics CRM. OData V4.0 was officially approved as a new OASIS standard in March, 2014 and was submitted by the OASIS Open Data Protocol members for a 30-day public review.
The OASIS OData Standards and Design Principles
The protocol supports the description of data models and the editing and querying of data according to those models. It provides facilities for metadata, data, querying, editing, operations and vocabularies.
The OASIS OData Version 4.0 follows these design principles:
1) Prefer mechanisms that work on a variety of data stores. In particular, do not assume a relational data model.
2) Extensibility is important. Services should be able to support extended functionality without breaking clients unaware of those extensions.
3) Follow REST principles.
4) OData should build incrementally. A very basic, compliant service should be easy to build, with additional work necessary only to support additional capabilities.
5) Keep it simple. Address the common cases and provide extensibility where necessary.
[Source: The OData Version 4.0 Part 1: Protocol]