In the name of brevity, this AIP defines some common terminology here rather than in each AIP individually.


The following terminology should be used consistently throughout AIPs.

API : Application Programming Interface. This can be a local interface (such as a client library) or a Network API (defined below).

Network API : An API that operates across a network of computers. Network APIs communicate using network protocols including HTTP, and are frequently produced by organizations separate from those that consume them.

Google API : A Network API exposed by a Google service. Most of these are hosted on the domain. It does not include other types of APIs, such as client libraries and SDKs.

API Definition : The definition of an API, usually defined in a Protocol Buffer service. An API Definition can be implemented by any number of API Services.

API Version : The version of an API or a group of APIs if they are defined together. An API Version is often represented by a string, such as "v1", and presents in API requests and Protocol Buffers package names.

API Method : An individual operation within an API. It is typically represented in Protocol Buffers by an rpc definition, and is mapped to a function in the API in most programming languages.

API Request : A single invocation of an API Method. It is often used as the unit for billing, logging, monitoring, and rate limiting.

API Consumer : The entity that consumes an API Service. For Google APIs, it typically is a Google project that owns the client application or the server resource.

API Producer : The entity that produces an API Service. For Google APIs, it typically is a Google team responsible for the API Service.

API Backend : A set of servers and related infrastructure that implements the business logic for an API Service. An individual API backend server is often called an API server.

API Frontend : A set of servers plus related infrastructure that provides common functionality across API Services, such as load balancing and authentication. An individual API frontend server is often called an API proxy.

Note: the API frontend and the API backend may run next to each other or far away from each other. In some cases, they can be compiled into a single application binary and run inside a single process.

API Service : A deployed implementation of one or more APIs, exposed on one or more network addresses, such as the Cloud Pub/Sub API.

API Service Name : Refers to the logical identifier of an API Service. Google APIs use RFC 1035 DNS compatible names as their API Service Names, such as

API Service Endpoint : Refers to a network address that an API Service uses to handle incoming API Requests. One API Service may have multiple API Service Endpoints, such as and

API Product : An API Service and its related components, such as Terms of Service, documentation, client libraries, and service support, are collectively presented to customers as a API Product. For example, Google Calendar API.

Note: people sometimes refer to an API Product simply as an API.

API Service Definition : The combination of API Definitions (.proto files) and API Service configurations (.yaml files) used to define an API Service. The schema for Google API Service Definition is google.api.Service.