Building Web APIs seems still more an art than a science. How can we build APIs such that generic clients can easily use them? And how do we build those clients? Current APIs heavily rely on out-of-band information such as human-readable documentation and API-specific SDKs. However, this only allows for very simple and brittle clients that are hardcoded against specific APIs. Hydra, in contrast, is a set of technologies that allow to design APIs in a different manner, in a way that enables smarter clients.
The foundation is laid by the Hydra Core Vocabulary. It defines a number of fundamental concepts, such as hypermedia controls and collections, which allow machines to understand how to interact with an API. Since all information about the API is available in a machine- readable form, completely generic clients become possible. The Core Vocabulary is complemented by Linked Data Fragments, a set of specifications that enable advanced yet efficient client-side querying of Web APIs.
To participate in the development of these specifications please join the Hydra W3C Community Group.
More information about Hydra is available at http://www.hydra-cg.com/