3.2 Application Programming Interface (API)¶

In the context of communication between external systems and TDH, two modalities of interchange are defined:

• RESTful web API (recommended),
• Web Services on standard SOAP, whenever the systems do not entail the use of RESTful web API.

API (Application Programming Interface) means “a set of protocols / functionalities / definitions through which it is possible to create integrated application systems; in this sense, the API is conceived as a «black box», namely a callable function for which it is only necessary to know its interface, without the need to know any implementation details [1]”.

Web APIs are APIs that can be called up from the Web (mainly based on HTTP protocol), whose goal is to obtain a high level of abstraction that mediates between the logic layer and the clients requiring its service. Web APIs are mainly of the REST type or of the SOAP type.

The data format for the SOAP Web API (or SOAP Web Service) is XML, while for the RESTful web API it is possible to leverage the formats provided by the HTTP protocol as defined by the W3C.

In the context of the RESTful web API, reference is made to the REST architecture, according to the Richardson maturity model [2]; in this sense, the RESTful model is compliant with level 3 of maturity - Hypermedia Controls.

The Guidelines identify the ways in which developers / adherents to TDH022 implement their APIs, as basic technological elements through which it is possible to establish the interconnection with the TDH and the use of services and / or contents by end users.