3 Terminology

Terminology used within this specification.

Term	Description
Message	The Message is the main entity of communication in this Building Block, it holds all the necessary information to deliver the information to the Publisher or to the Subscriber/client, leaving just a track of delivery Logs with no personal data included. Messages follow a predefined protocol and policy for the chosen or predefined Communication channel. As a rule, the delivery mode of the Message is asynchronous.
Publisher	This is the originator of the Message, holding information about the content of the Message and the (meta) data regarding the Subscriber who will receive the Message. In other words, Messaging Building Block proxies/relays the Message received by a Communication channel to the proper Subscriber/client/person.
Subscriber	In the Publish and Subscribe use case, where the Publisher is relaying the Message into the hands of Messaging Building Block, that will in turn route it to the desired Communication channel, the Subscriber is the one who is listening to the relevant Message Room to receive the Message from the Publisher. The Subscriber has given consent to the Publisher to access or retrieve and store its data for the purpose of carrying out the Messaging event.
Messaging event	Messaging event is the (single) act of asynchronous information transfer between the Publisher and the Subscriber, consisting of the following steps: 1) secure identification and access management of the Publisher and the Subscriber; 2) access to and/or retrieval of relevant Subscriber data and consent for using the data from the Subscriber; 3) selection of relevant data transfer policy and protocol for the Messaging event; 4) Management and processing of Logs and relevant metadata during and after the Messaging event.
Messaging protocol	It is the protocol enabling the Messaging Building Block to communicate and transfer data between appropriate endpoints. N.B. In its initial versions, GovStack Messaging Building Block is using Matrix/Elements protocol as a reference point for creating the GovStack Messaging Building Block protocol.
Communication channel	It is the endpoint of the Message delivery, the means used by the Publisher or the Subscriber to communicate. It can be a social media tool, e-mail or SMS service, or a distributed network.
Log	It holds track of Message delivery with the encrypted content to help with the maintenance and troubleshooting of the messaging services.
Routing Policy	Routing policy is the essential, configurable service of the Messaging Building Block, published in the Information Mediator Building Block, and is enabling the Publishers and the Subscribers to pre-define and use the appropriate Routing Policy for the particular Messaging event. In future iterations of this specification, the Routing Policy can be applied to the Messaging Rooms.
Service provider	Service providers provide service(s) to End clients. For example, medical doctors, hospitals, government agencies, etc. In some cases, a Service provider can also be in a role of an End client, being served by another Service provider.
End client	In most cases, End clients are citizens of any given country contacting and/or requesting or being served by a Service provider. For example, a mother/caretaker of a newborn child being serviced by a Health Care Service provider.