7 Data Structures

This section provides information on the core data structures/data models that are used by this Building Block.

The resource model shows the relationship between data objects that are used by the Information Mediator Building Block. The data elements provide detail for the resource model. All data element schemas can be viewed, commented on, and modified in the schemas section of the Information Mediator Building Block GitHub repository.

7.1 Resource Model

The Mediator Building Block key element is Service. The Service is used by a consuming Building Block or an application and offered by a provider Building Block or Application. Both Provider and Consumer must be Members of the Mediator Building Block. Members of the Information Mediator Building Block can be an organization (governmental or not, business or not) or a person (citizen as a rule).

Diagram source

To become a Member of Mediator Building Block participants must fulfill declared requirements and apply for onboarding. In the process of onboarding a Member is registered with Mediator Building Block and gets credentials to connect to Mediator Building Block. Normally it is done the way that a Member provides a certificate of recognized Certification Authority (CA), and requests signed with this certificate are considered legitimate requests of the Member. A member entity can access the Pub/Sub configuration and register a room to publish its own event type as a publisher through its own admin.

Members can browse a directory of Services available in the Mediator Building Block. Each service is described in OpenAPI.

7.2 Data Elements

7.2.1 Member

Fields:

Name	Type	Description
class	enumerator	namespace for member_code, e.g. GOV or COM
code	string	unique id of member in registry defined by member_class
signing_key	string	name of key used to sign on behalf of Member
certificate	certificate	certificate of member issued by trusted CA

Schema reference member.json

7.2.2 Application

Fields:

Name	Type	Description
code	string	unique name of application in member scope
connection_type	string	protocol used for connection: http or https
certificate	certificate	TLS certificate

Schema reference application.json

7.2.3 Service

Fields:

Name	Type	Description
code	string	unique name of OpenAPI in scope of application
description_url	url	location of OpenAPI service description
service_url	url	service provisioning network address
ACL	object	description of access rights

Schema reference service.json

7.3 PubSub Layer

7.3.1 Resource Model

The Resource Model is an extension of the Access Layer model:

Diagram source

7.3.2 Data Elements

7.3.2.1 Event

An event is a message—a set of data sent to a topic. Each event has an id. The event corresponds to the message. Data elements of an event are described by event type OpenAPI description.

7.3.2.2 Event Type

An event type is schema definition for an event. Each event type is owned by a Room of a certain authority. (E.g. the Ministry of Health might own Room with the “new_birth” event type and define its schema.)

7.3.2.3 Publisher

A candidate application playing the role of IM-Publisher must be able to emit events to a specific Room.

Data Element	Default format	Description
id	string	application id of this publisher
name	string	OPTIONAL

7.3.2.4 Room

(N.B., this is often called a "topic" and we may shift to that in later versions.)

A candidate application playing the role of IM-Room must handle the distribution of events. Each Room has a set of connected event types (e.g., the “birth” room might contain three event types: “new_birth”, “birth_complication”, and “infant_death”). A room is located in the member’s local Information Mediator Building Block implementation and the member is responsible for all types of events in that particular room.

Data Element	Default format	Description
id	string	application id of this room
name	string	OPTIONAL

7.3.2.5 Subscriber

A candidate application playing the role of IM-Subscriber must be able to process events. It is done by defining a Service that will be called by Room to deliver an event. Subscribers are independent of each other and their business logic differs (as a rule). Each subscriber processes events from their own perspective.

Data Element	Default format	Description
id	string	application id of this subscriber
name	string	OPTIONAL

7.3.2.6 Subscription

Data Element	Default format	Description
id	string	subscription id
room_id	string	room id
subscriber_id	string	subscriber id
event_type	string	A filter expression that allows a subscriber to subscribe to only certain message_types that are published to the room they're subscribed to.
mode	enum	delivery mode
details	object	details of delivery, like time to live, repetition policy, etc.