RESTful Web APIs

Glossary

application semantics

A representation’s application semantics explain the underlying resource in terms of real-world concepts. Two HTML documents may use exactly the same tags but have completely different application semantics—one of them describes a person, and the other describes a medical procedure.

If a document format is designed to represent real-world concepts, we can say the format itself has application semantics. The Maze+XML format has the application semantics necessary to represent maze games. The HTML format has the application semantics of a human-readable document. The HAL format has no application semantics to speak of: each user must supply their own.

The term “application semantics” was invented for this book. It’s not a standardized term.

application state

Information about the client’s path through an API is application state. Most clients start in the same state, at an API’s “home page.” As they make different choices, they trigger different hypermedia controls, they end up in different places, and their application states diverge.

cache

A repository of HTTP responses, used to improve client performance. A client can sometimes reuse a cached response instead of sending a request over the network.

code on demand

One of the Fielding constraints. This one says that the server may send executable code in addition to data. This code is automatically deployed on the client and can change along with the rest of the server implementation. ...