This document defines the framework, function and protocols for an API ecosystem that will enable online synchronised interaction. Specifically, the document:

— defines a logical and technical layered approach for developing APIs, including transformational rules. Specific logical models (such as ISO 20022 models) are not included, but they will be referenced in the context of specific scenarios for guidance purposes;

— will primarily be thought about from a RESTful design point of view, but will consider alternative architectural styles (such as WebSocket and Webhook) where other blueprints or scenarios are offered;

— defines for the API ecosystem design principles of an API, rules of a Web-service-based API, the data payload and version control;

— sets out considerations relevant to security, identity and registration of an API ecosystem. Specific technical solutions will not be defined, but they will be referenced in the context of specific scenarios for guidance purposes;

— defines architectural usage beyond query/response asynchronous messaging towards publish/subscribe to support advanced and existing business models.

This document does not include:

— a specific technical specification of an API implementation in financial services;

— the development of JSON APIs based on the ISO 20022 specific message formats, such as PAIN, CAMT and PACS;

— a technical specification that is defined or determined by specific legal frameworks.