Subscription and Notification Pattern

The pattern is used by the Doing Business Abroad Pilot in Use Case "Doing Business in Another Member State" (DBA UC2).

After receiving evidence from a Data Owner (DO), it can be essential for a Data Evaluator (DE) to be informed on changes regarding the subject of this evidence to be able to take appropriate action. The goal of this interaction pattern is to allow the DE to subscribe to a service of the DO that provides automatic and regular notifications. The cross-border message exchange for the subscriptions and notifications are put in the responsibility of the Data Requester (DR) and the Data Transferor (DT) respectively to allow an easier distribution of responsibility on national level, i.e. to intermediary platforms and national gateway providers.

Functional Variants of the Subscription and Notification Pattern

There are two distinct purposes, or business requirements for Subscription and Notification, both of which are relevant for the DE4A Doing Business Abroad Pilot: Evidence update notification and Event notification.

Evidence Update Notification

The goal is to keep previously shared evidence data that is stored at the DE up to date.

Description: Data may change in the base register. In case the DE wants an exact copy of the evidence data on record, they need to be notified in case the data has changed in the base registry.

Business or Life Event Notification

The goal is to assess the impact of changes to the subject (e.g. company) on the public services provided by the data evaluator.

Description: Some public services oblige the subject (i.e. company or citizen) to continue in a specific situation or state to remain entitled to the benefits of the public service provided. An agricultural company may, for example, receive a subsidy for its permanent pasture. As a prerequisite, the company must preserve the pasture for five consecutive years. The data evaluator needs to be notified of the company ending its operations and hence not meeting the five-year requirement. “Ending its operation” is an example of a business event. Other examples are: going bankrupt, a merger, etc.

Alternative Solution Approaches

Essentially there are two ways to approach the dual requirements for Subscription and Notification, either specific solutions for each requirement or hybrid approaches that can serve both.

Looking at specific solutions means that two specialized systems would need to be developed and implemented:

1. Specific Evidence Update Solution: The subscription would be linked directly to the previously exchanged evidence, hence the subscription would need to register the evidence type, the subject ID and the subscriber ID. For any data change in the evidence type data set at the DO, the DP would need to push a complete new evidence to the DC, irrespective of that specific change being relevant for the public service provided to the user by the DC. Apart from this being not optimal from a data minimization principle perspective, it can not cover changes of the subject that are not represented in the evidence type data set, giving rise to the need of a second subscription system for events. In addition, the subscription system would be impacted by changes in the canonical evidence type definitions over time. This approach might, however, be easier to integrate in the legal framework of the SDGR (see Legal Considerations below).
2. Pure Event Notification: The subscription is not directly related to a previously exchanged evidence, but the subscription could be registered for an agreed set of events relating to a given subject. The subscription system would consequently be based on a list of events, rather than a list of evidence types. Quite obviously, this requires an agreement on a set of DE4A events, or canonical cross-border events.

Technical approach and business requirements do not relate one to one, giving rise to several hybrid approaches, where one solution is used to cater for both requirements:

1. Extended Evidence Type: The Specific Evidence Update can be used to derive relevant Events at the DC, if the evidence type definition is scoped, or extended, so that all relevant events are represented by data changes in the evidence type data set. This would require the DC to run an event identification routine (either immediately or periodically) after receiving updates in order to react accordingly. The extension of evidence type definitions beyond what is actually required by the eProcedure is, again, not optimal from a data minimization principle perspective. This hybrid solution can not resolve events that are dealt with by procedural means at the DP-side, rather than by data mutations.
2. Extended Notification Message: The pure Event Notification could be extended to carry an updated evidence as part of the Notification message, essentially piggybacking the evidence onto an event notification. This approach would need to extend the event-centric subscription system to maintain with underlying evidence type, or potentially multiple evidence types, are relevant for each event type, so that evidence can be retrieved and packed as extension of the Notification Message. Which evidence is required for which event can additionally differ by public service provided and hence per subscriber. This solution would consequently end up to be rather complex and again not optimal from a data minimization principle perspective. [A BPMN Process Analysis of this approach is available on request]
3. Event Notification + Lookup: The pure Event Notification is used as described above, while it is made sure that the agreed event set of canonical DE4A events is complete in the sense that in covers also relevant update needs, for example a company that moved HQ means that the address (part of the Company Registration evidence) changed as an effect. It is then left at the discretion of the DC, whether a particular event requires an update of the evidence on record. It could be that, i.e. the postal address of a company is not relevant for the continuation of the public service provisioning, in which case a flag that the address on record is not up to date, or a change to "unknown" would be sufficient as event response. This is fully in line with the data minimization principle perspective. If the DC considers that an update of one evidence or potentially several evidences is required as part of the event response, then the DC would use the Lookup Pattern to request new copies of evidences if and when required. The effort needed to make this approach work for evidence updates mostly concerns the Notification process: The DP might need to add "weak" events to their platform to cover changes that are not considered relevant enough to be in their event list yet, e.g. change of e-mail address. The DC will need to define or extend a decision table that relate event type to public service and returned the correct action to be taken, i.e. request a new evidence via the Lookup Pattern.

The reference Architecture for the DE4A projects focusses on the third option, the combination of Event Notification and Lookup Pattern to cover both business requirements with one hybrid solution, rather then setting up two specific solutions next to each other. The combination of Event Notification and Lookup Pattern appears to be the most flexible approach is expected to have the following advantages:

• Data minimization: Evidences are only requested if they are actually needed for the public service provided by the DC
• Low complexity of message definitions: The required message definitions for the notifications and updates between DP and DC remains low in complexity: A simple event notification (consisting of event type, identifiers and timestamp) and evidence response analogous to the event response message of the Intermediation Pattern and User-supported Intermediation Pattern.
• Multiplicity: Case that single events require multiple evidences to be updated, or several events require the update of the same evidence can be covered quiet easily without requiring complex message definitions.
• Flexibility in legal basis and authorizations: As the Event Notification does only contain identifiers and not the underlying (personal) data (which requires the eIDAS revision to create a European Unique Identifier for natural persons), the legal basis and corresponding authorizations might differ between Notification and Lookup, adding flexibility to the overall solution.
• Independence from a previously shared evidence: The solution approach is not directly linked to a previously shared evidence, which means that a subscription and subsequent lookup can also be applied in cases where the original procedure (leading to the public service being provided) was completed without any automated evidence exchange, i.e. evidence was provided by the user electronically or in person, provided that there is a legal basis (see below).
• Extension of scope: New events can be added flexibly without immediate impact on existing subscriptions and without maintaining different versions of an (canonical) evidence definition.

Working hypotheses and implementation principles

Subscription and Notification Pattern working hypotheses and implementation principles

Interdisciplinary Topic	Hypothesis / Principle	Implications and Limitations
Orchestration / Choreography	Subscription: The DC controls the overall flow for the subscription. This means that the process on DP side is a child process of the process on the DC side. Notification: The Notification is conceived as a "fire and forget" coinversation, meaning that the processes are not really orchestrated. The DP process triggers (if successful) the DC process.	If issues on the DC-side (subscriber) prevented receiving notifications, a resubmission would need to be requested explicitly. The DP required functionality for such (manual) resubmission of notifications.
Interrupted vs. Uninterrupted exchange	Both the Subscription and the Notification are considered to be uninterrupted, not sending any deferred responses.	For the subscription, this means that the DC must assume that the subscription was not successful if not receiving a confirmation delay. For the DP, this means that their subscription system must be robust against receiving the same subscription twice.
Encryption Gap	OOP in the public sector does not require true E2E encryption. The exchange between DR and DP must be encrypted and signed, as well as the transfers (if applicable on national level) between DR and DE on DC side and DT and DO on DP side (i.e. using the national OOP layer), but the encryption gap within the systems of the DR and DT is acceptable.	This might not hold for cases where the gateway would be outsourced to a private sector subcontractor, which is not foreseen for the DE4A pilots.
Automated re-use of data	Subscription and Notification are structured and adhere to known semantics and format that allow fully automated processing after receipt.	To facilitate automated re-us of data requires establishing canonical event definitions.
Production system and real-life cases	If the events relate to a legal person, not a natural person, subscription and notification can be run in production environments (see: Legal Considerations below)	The DC still needs a legitimate reason to subscribe to events of a subject (i.e. company)
Payment for evidence	In the context of the pilots we assume that no payments are required.	This can restrict transition of pilot solutions to production in cases that competent authorities require payment for issuing evidence.
BRIS integration	A technical re-use or bridge to BRIS is not possible because of differences in scope and accessibility by competent authorities other then business registers.	The pilot system for the Doing Business Abroad Pilot need to be set-up separate from BRIS.
Matching evidences between Member States	The Event Subscription and Notification is based on a set of harmonized events definitions.	The participants need a semantic agreement in a set of standardized life/business events.

Legal Considerations

From a legal perspective, the central challenge is the need for a legal basis that allows impacted authorities to exchange Evidence Updates and/or Event Notifications. This is certainly critical for personal data (since the GDPR requires a legal basis), but even in the case of pure business data that contains no personal data, authorities will need to be able to demonstrate that they have a legal basis allowing them to send Evidence Updates and/or Event Notifications abroad.

The SDGR is in principle not an answer to this issue, since it focuses on user-driven exchanges (based on a user request, and with a preview option). While a user request could have been scoped in a way that allows a user to define a time period for exchanges ('I request authority A to send evidence X to authority B, including any updates, for a period of Y years'), this is not the implementation path that has been chosen in the Implementing Act. Moreover, such a request wouldn't enable a preview as the SDGR requires. Thus, referring to the SDGR is not a sufficiently encompassing option.

This does not imply that subscriptions or event notifications are impossible, but rather than an alternative legal basis must be found. A few options are available, which will be discussed briefly below. For the avoidance of doubt: these options should only be applied in relation to business data; subscriptions/event notifications relating to individual persons (citizens) do not have a clear legal basis under data protection law, and due to the public sector context, reliance on consent or legitimate interest of the public administrations is not legally feasible.

For business data subscriptions and event notifications, the following options would be available:

- there should be no legal challenge in principle if the relevant information is already made publicly accessible by the relevant authority. If the information can be freely accessed and lawfully used by the public, proactively communicating it to specific authorities (in the form of evidence or a notification) should not be problematic either. While typically some terms and conditions would apply even to publicly accessible databases (e.g. to forbid commercial exploitation), it would be possible to conclude comparable agreements in the context of DE4A as well.

- exchanges should similarly be possible for information that is not publicly available, but that can only be accessed and used by parties if they conclude a suitable agreement with the relevant business register. In some Member States, business register data is made available to commercial entities on the basis of (usually) paid contracts, e.g. allowing them to integrate that data into business intelligence services. Companies can subscribe to such services to check e.g. credit rating or bankruptcy status of their customers. In countries that support this model, it should be legally feasible to conclude similar agreements to support DE4A pilot exchanges, hopefully on a free of charge basis, if this is acceptable to the data source.

These scenarios are likely more relevant for Updates of evidences than for pure Event Notifications, since formal evidences (extracts, certificates, attestations etc) are normally not included in these models.

Specifically for Evidence Subscriptions, the principal legal solution would be to establish a legal basis for the subscription outside of the SDGR. This could be viable under national laws, in combination with the request of a representative of the affected legal entity. A pure appeal to national law (without any request for a subscription service from the user) likely will not work; this is only possible if there's already a specific legal basis for direct evidence exchanges between the authorities, and that does not seem to be the case. The BRIS Directive is the closest approximation, but does not provide a basis for evidence subscriptions. This is why the request is important, as a way to strengthen the legal mandate of the evidence provider, allowing them to build on any existing right of the company representative to obtain evidences in relation to their company.

Business Process of the Event Subscription and Notification Pattern

The subscription and notification pattern realizes the goal to inform the data evaluator of relevant changes in the subject (i.e. company or citizen). This is done in two steps:

1. In the subscription step the DE expresses the need to be informed on changes regarding a certain subject and this need is registered as a subscription.
2. In the notification step the DO monitors the subject and if a change occurs, all subscribers will be informed on this change

These two steps are independently triggered processes and are hence represented below in two separate BPMN Business Process Collaboration views. Please note that the Subscription is triggered by the DC (i.e. DC is the upper participant in the Subscription BPMN diagram), while the Notification is triggered by the DP (i.e. the DP is the upper participant in the Notification BPMN diagram).

Event Subscription and Notification Starting Points

Some high-level starting points for the process design of this pattern are:

• Harmonised DE4A events: a list of harmonised, canonical events needs to be agreed upon so DE knows how to interpret events notified by DO. For the DE4A-pilots, i.e. the Use Case "Doing Business in Another Member State" (DBA UC2), it is an option to start with a short list of harmonised business evens.
• Subscription registration: the subscription consists at least of the subject identifier and the subscriber identification (i.e. DE ID).
• Business- or Life event-based notification: the event-based approach informs the DC, i.e. the subscriber, of every business of life event of the subject (i.e. company or citizen) subscribed to. Examples of such events: address changed, new owner, bankruptcy, employed/unemployed, death.
• Notification message: the notification consists at least of the subject (i.e. company) identifier, the harmonised event type of the event that took place and the timestamp of the event.
• Data evaluator post-processing: the DE needs to interpret the event and decide on the actions needed: e.g., request updated data, discard notification, start a specific procedure.

Event Subscription

Business Process Collaboration

The BPMN diagram below shows the Business Process Collaboration of DC and DP that starts with the need for a subscription being identified (i.e. in a public service procedure) and leads to the DE logging the confirmation that their subscription was successful.

Event Subscription Business Process Collaboration View

The DE initiates the subscription and lets the DR identify the correct DO and sending the sub subscription request. Please note that a change of an already existing subscriptions follows the same process; The subscription end-date would, for example, be changes to effect a cancellation or prolongation of a subscription. The option of a perpetual subscription with explicit cancellation was also discussed and discarded. The DP process registers the subscription and returns a confirmation or an error (in case the subject could not be found in the registry). The Table below provides a description of each of the activities in the process.

Activity Table

Activity / UC	Role	Activity Type*	Description
Trigger: Need for a subscription identified	Public Service Procedure	Process	A procedure of a public service provider (e.g.: subsidy) leads to the registration of a subject (e.g. company). After this registration, events can occur to the subject that could have impact on the service delivery to this subject. In order to be informed on these events, the public service provider can subscribe to the life-events or business-events of the subject. The subscription process can also be triggered for technical reasons: for instance to resend failed subscription requests. E.g.: In the pilot Doing Business Abroad the subject is the represented company itself or a new branch of the represented company (the parent-company of the branch) and Data Evaluators subscribe to be notified on the business events of the represented company.
Trigger: Change subscription	eProcedure / Public service / Notification	Process	Potential triggers to change a subscription are: Public service: public service delivery can lead to the need to cancel the subscription (the public service has ended, e.g. a multi-year subsidy procedure, the country can decide to cancel the branch-office registration). eProcedure: the user can also withdraw from service and thereby initiating cancellation of the subscription. Notification: after receiving a notification the assessment can be that the subscription is no longer needed (exception flow). Technical reasons: for instance an error at the DO-side could lead to the need to resend the request to cancel a subscription.
Initiate subscription	DE	Service	To initiate subscription data is collected and the subscription need is formulated: subject identifier data owner identifier subscriber identifier event catalogue action 'subscribe' subscription start and end date The subscription need is forwarded to the Data Requestor.
Change subscription	DE	Service	To change a subscription data is collected and the changed subscription need is formulated: subject identifier data owner identifier subscriber identifier event catalogue action 'cancel subscription' new subscription end date The cancellation of a subscription is thus a change of the end date the current date. The changed subscription need is forwarded to the Data Requestor.
Lookup event provider routing information	DR	Service	The DR uses the data owner identifier to look up routing information of the competent authority that facilitates subscription service. It is possible that at the DP-side the service provider of the subscription is different from the service provider of the evidence.
Send subscription request	DR	Service	The request to subscribe is send to the participant facilitating the subscription service using the previously retrieved routing information. The subscription request contains: the participant id of the subscriber, the subject identifier, the event catalogue, the period of subscription and the requested action (subscribe / cancel subscription).
Validate subscription request	DT	Service	The request is validated on a technical level and check on DE authorisation. If the request validates it is forwarded to the Data Owner. [Technical exceptions are out of scope.]
Evaluate subscription request	DO	Service	The subscription request is evaluated to check if the request can be completed: Subscription functional checks: does subject exists, is event catalogue supported, is the subscription changing an existing subscription (i.e. update) If the request does not pass the functional checks, the request is rejected and an error message will be sent.
Exception: Prepare subscription error message	DO	Service	Collect the content of the error message and send it to the Data Transferor. The subscription error message contains: participant id of subscriber, subject identifier, requested action, reference to the request message, full request message and the error code.
Exception Send subscription error message	DT	Service	The error message is forwarded to the Data Requestor from whom the request was received.
Exception: Forward subscription error	DR	Service	The subscription error message received from Data Transferor is forwarded to the Data Evaluator.
Exception: Investigate reason for subscription error	DE	User	The received error message is analysed and appropriate actions are taken. This exception flow is not further detailed in this design.
Register subscription	DO	Service	The Data Owner creates or changes the subscription according to the subscription request.
Confirm subscription	DO	Service	The confirmation of the subscription is created and send to the Data Transferor. The confirmation message contains: subscription result (success), timestamp of subscription, subscription request reference, subscription id.
Send subscription confirmation	DT	Service	The subscription confirmation is sent to the Data Requestor from whom the request was received. The subscription confirmation message is added to the log.
Forward confirmation	DR	Service	The confirmation of the subscription (received from the DT) is forwarded to the Data Evaluator.
Log subscription information	DE	Service	The confirmation is logged to complete the audit trail. Note: register in a way that it is easily readable (optional: include subscription id).

*Activity Type and Task Type in accordance with BPMN 2.0

Design decisions

Explicit request and preview

The nature of the Subscription and Notification pattern leads to a different use of the explicit request and preview as stated in the SDG Regulation:

• Notification is performed without a user involvement, making real-time explicit request and preview impossible.
• Fraud prevention is an important driver for notifications, making explicit request and preview less opportune.
• The public nature of company data relaxes the need of explicit request and preview.

Implementing an explicit request for future notifications introduces the burden of creating and maintaining an explicit request administration or even management of consent, with for instance options to revoke a previously given consent - these are arguably more relevant for citizen use cases.

Design decision: for the Business event notification explicit request and preview as defined in the SDG Regulation is not applicable.

Positioning of subscription registration

For the location of the subscription registration various options can be considered:

• At the data providing MS: The subscription is registered at the data providing member state. The DE sends messages to the DO via DR and DT to manage the subscription (subscribe, cancel subscription).

• Split between data provider and data consuming MS: It is a possibility to split the register; the DO then only registers which MS subscribe to a certain company, and the DC MS registers which DE subscribe to the company. The process flow would be: (1) a central component at the DT registers which DEs subscribe to which subjects of which data owners; (2) the DT registers as a MS for this company; (3) the DO registers which MS subscribes to which company and sends notifications to the DT (4) the DT distributes the notification to all DE.
• At a central component: The DE4A architecture implements the four-corner model, a central subscription register would conflict with this principle. Moreover, a subscription is a direct relation between a DO and a DE regarding a subject, there will be no added value to place such a subscription in an external, central component.

Design decision: The registration of subscriptions is placed within the data providing member state. DP MS is free to choose in which environment this is (DT, DO or another environment). The assumption for the design of the S&N pattern is that the subscription registration is fully placed in the environment of the DO.

Subscription period

Both perpetual subscriptions and the use of a subscription period with start and end date were considered. A perpetual subscription would require an explicit cancellation from the DE if the subscription is not needed anymore. This option was discarded, mainly because of the risk of an increasing number of "ghost subscriptions" that send automated notifications that are then automatically filtered out as irrelevant upon receiving.

Design decision: a subscription period with mandatory start and end dates is included in the subscription.

Evidence exchange and subscription request

The main flow of the DBA pilot is that the intermediation pattern triggers the subscription and notification pattern. Part of the intermediation pattern is the exchange of evidence: DE requests a specific evidence type from a specific company from the DO. In the happy flow the DE subscribes to receive notifications regarding this company. This trigger can be implemented in different ways:

• As a part of the request for evidence. The evidence exchange request then consists at least of: company identifier, requested evidence type, DE identifier, subscribe y/n.

• In a separate subscription request message: after a user consent to the preview and a successful completion of the registration process a separate subscription message is sent.

Design decision: the subscription request is not combined with the evidence exchange request but is sent after successful registration of the company/branch.

Design decision: not all business events are related to an evidence, subscriptions must therefore be made to business events to cover all notifications to be sent

Event Notification

Business Process Collaboration View

The BPMN diagram below shows the Business Process Collaboration view of the Event Notification process that starts by analysing domestic event definitions from a Registry (considered external to this process) and concludes with the DE logging the appropriate action to be taken as result of the notification. Pleas note that the process starts with the DP, hence the upper pool in the diagram is the DP.

Business Process Notification View of the Notification Process

As can be seen in the Figure above, the Notification is not expecting any business-level confirmation. The DP filters events from the registry that are relevant for cross-border notifications and the DT sends them to the DC. The set of harmonized events allows for an automated processing of the notification and the identification of the correct action. These actions are not only dependent on the type of event (identified by the DP), but also the type of public service provided by the DC. A simple response would be to lookup a changed evidence (see Lookup Pattern). More complex cases will require a business response and expert analysis. The reference process informs the responsible organisation or department to come into action.

Activity Table

Activity / UC	Role	Type	Description
Identify event	DO	Service	The Data Owner evaluates all events identified in the register and identifies events that are potentially relevant for cross-border notifications. Note that the DO must have a mapping of it's own business events to the list of DE4A business events.
Check subscriptions	DO	Service	The subscription register is queried for subscribers to the subject (e.g. company) related to the event: No active subscriptions: end of process Active subscriptions for the DE4A event catalogue found: continue notification process
Prepare notification message and subscriber list	DO	Service	Make a list of the subscribers to notify in terms of cross-border participant identifiers and create the payload of the notification, mainly the DE4A event name and subject identifier and the timestamp the event took place.
Exception trigger: Request from DE to resend event notifications	DE	User	Exception flow for missed notifications (failed or non-failed): if a DE misses notifications a resend of notifications can be requested.
Exception: Resend past events	DT	User	The resending of previously sent notifications requires a manual action at the DT, based on logs.
Resolve service metadata	DT	Service	Single notifications messages (one for each subscriber) are created from the list of subscribers and the notification payload. The routing information for each notification message is looked up. The messages contain: subject identifier, secondary subject identifier (in case the identifier changed), subscriber identification, event identification, event timestamp, subscription reference (optional).
Exception: Resolve subscriber participant ID and inform National Contact Point	DT	User	If address / DE participant ID is not found in the metadata, manual action is needed: contact DE / MS of participant to analyse the exception and take appropriate measures.
Send event notification	DT	Service	The event notification is sent to the Data Requestor, a technical acknowledgement that the notification has been received by the DR is received. The audit log is updated with both the event notification and the acknowledgement.
Validate event notification	DR	Service	The Data Requestor performs a technical validation of the event notification and forwards it to the Data Evaluator. A technical exception flow is out of scope of this process description.
Determine event response	DE	Service	The notified event is analysed, and the appropriate response is determined. Depending on the event, different courses of action are possible: Event is not relevant Event requires a new (i.e. updated) evidence Business response required Exception: The notification does not match the record or the record is not active, hence the subscription needs to be changes (i.e. cancelled) The determination result is logged as a part of the audit trail: Subject identifier Notified event Request ID Determined response Timestamp of determination
Request change of subscription	DE	Subprocess	When the company cannot be identified, or the registered company or branch is no longer active, a change (i.e. cancellation) of the subscription is requested. Afterwards this will be analysed to find the cause of this apparently wrong subscription and to take appropriate measures. This subprocess includes user tasks and is not end-to-end automated.
Dismiss event	DE	Service	The notified event does not have impact on the procedures of the Data Evaluator and is dismissed. No further actions need to be taken.
Trigger evidence lookup	DE	Service	The Lookup Pattern is triggered to request a new, current, copy of the relevant evidence. The Doing Business Abroad Pilot will e.g.: request the Company Registration Evidence.
Identify business response and notify responsible party	DE	Subprocess	The responsible organisational unit is identified and informed in order to take appropriate action. It depends on the specific process if this action can be performed automated or manually.

Design decisions

Response on event notification

Functional responses from Data Evaluator to Data Owner after receiving an event notification, for example to inform that appropriate actions have been taken, are out of scope of the Subscription and Notification pattern.

Notifications from Subscriber

Notifications from Data Evaluator to Data Owner, for example to inform Data Owner on changes in the branch registration, are out of scope of the Subscription and Notification pattern.

Process Realisation

As with the Business Process Collaboration Views above, the Subscription & Notification pattern has two sets of Process Realization Views that provide the details on functional Application Services required to realize the business process.

• Two Views concerning Event Subscription, starting with the view for the DC, as it is the DC that starts a Subscription
• Two Views concerning Event Notification, starting with the view of the DP, as it is the DP that starts a Notification

This pattern does not provide any User Process Realization views as the user is not directly involved in the exchange. As can be seen in the Business Process above, Subscription is triggered by a public service process that requires updates for as long as the public service is provided, and the Notification is triggered by Events identified in the Base Registry.

Please see to the respective sections per Application Collaborations in the Reference Application Architecture for detailed descriptions of each Application Service.

Event Subscription

The figure below shows the Process Realisation of the Subscription process at the Data Consumer, triggered by the need for a subscription, i.e. for public service provided over an extended period of time, and resulting (if successful) in receiving and logging the subscription.

Subscription Process Realization of the Data Consumer

The Process Realisation view above shows that both Initiation and Change subscription is provided by essentially the same service from the EProcedure Back-office. Changes, i.e. changes of the subscription end-date are handled in the process essentially identical as new subscriptions and are used to effect prolongations (new, later end-date) and cancellation (new end-data set to current date) of subscriptions. This provides maximum freedom to Cross-border Subscriptions systems of the DP to handle cancellations and prolongation in the context of their own application architecture. For update cases a reference to the original subscription could be included as optional attribute in the request message. Service from the Information Desk, the Trust Architecture and Data Logistics are used to address and send the subscription request to the right DP. Even if the DP identity might already be known, at least the technical rooting information is looked up, given the highly distributed nature of cross-border systems.

The right half of the Process realization shows reaction to receiving either a subscription error or confirmation. Investigating the reasons for a subscription error is a subprocess that usually includes manual work, as reasons can reach from simple ID mismatches to fraud.

Application Collaborations used by this Process Realization diagram:

• EProcedure Back-office
• Information Desk
• Trust Architecture
• Data Logistics

The figure below shows the Process Realisation of the Subscription process at the Data Provider, triggered by receiving a subscription request from the DC and resulting, if successful, by sending a confirmation that the subscription was registered in the Cross-border Subscriptions system.

Subscription Process Realization of the Data Provider

The Process Realisation view above shows that the process requires, apart from a simple technical validation, some sort of authorization at the start, the Authority Check, realized by the Information Desk. This is considered more relevant for Subscriptions than for the Intermediation Pattern, let alone the User-supported Intermediation Pattern, because the user is not directly involved here. The main part of the process is supported by a Cross-border Subscriptions system. This application collaboration realizes all Application services required to evaluate, register and confirm the subscription. Please note that the Subscription Creation and Update Service must identify whether a subscription request relates to an already existing subscription, i.e. is an update. This should happen at least as fall-back option, based on the subject ID and subscriber ID and overlapping subscription times, rather than a mandatory subscription ID, which could remain optional. In addition, Trust Architecture and Data Logistics are involved to guarantee secure and reliable message exchange.

Application Collaborations used by this Process Realization diagram:

• Cross-border Subscriptions
• Information Desk
• Trust Architecture
• Data Logistics

Event Notification

The Figure below shows the Process Realisation of the Notification process at the Data Provider, triggered by changes in the base registry and resulting, if successful, in sending a Notification to the DC.

Notification Process Realization of the Data Provider

The Process Realisation view above shows that the event stream from the base registry is first filtered to identify Cross-border events, i.e. events that are mapped to DE4A canonical event definitions. These events are then used to lookup active subscriptions, which are then collected into a subscriber list per event, coupled to the Notification Message (i.e. event type and subject ID). All of these steps are realized by the Cross-border Subscriptions Application Collaboration. The Information Desk is again used to lookup at least the technical part of the routing. This gives rise to an exception flow if for a subscriber, registered in Cross-border Subscriptions, no service metadata (i.e. consumer) can be found in the Information Desk. Resolving such a situation is a subprocess, involving manual work and often resulting in corrective action required at the subscriber-side (e.g: reorganisation in the DC country did not update subscriptions, service metadata not maintained). Finally, Trust Architecture and Data Logistics providing for secure messaging.

It is important to note that the DP Process ends with sending the actual Notification message. Even though the transport protocol should ensure that this Notification was received by the gateway of the DC, this still means that it is functionally a "fire and forget" exchange; The DP is not informed whether the Notification was successfully processed by the DC. This gives rise to a second starting point of the process for exception handling: The DT might be asked by a DC, who experiences problems receiving or processing notifications to have all notifications (both successful and unsuccessful) of a given time period to be resent from the logs.

Application Collaborations used by this Process Realization diagram:

• Cross-border Subscriptions
• Information Desk
• Trust Architecture
• Data Logistics

The Figure below shows the Process Realisation of the Notification process at the Data Consumer, triggered by receiving an Event Notification message and resulting in the correct event response being triggered and logged.

Notification Process Realization of the Data Consumer

The Process Realisation view above shows that Trust Architecture and Data Logistics play again their role in secure message exchange, while the EProcedure Back-office plays the central role in determining the event response and in triggering the associated actions.

• For the hybrid approach described above, a lookup of an evidence (i.e. company registration) could be triggered.
• Changing or cancelling the subscription
• Notifying the responsible organisation to take actions (e.g. termination of public service, suspicion of fraud)
• No immediate reaction is required

Application Collaborations used by this Process Realization diagram:

• Trust Architecture
• Data Logistics
• EProcedure Back-office