Adxstudio Portals includes a custom activity entity called "Alert Subscription" (adx_alertsubscription). This activity can be linked to any Entity and When a record of that entity type is updated, can be linked to a workflow to send an email or SMS message to all subscribes of that record.
The Entity is a custom activity so that it can be linked to any entity that has actvities enabled. Out of the Box, Adxstudio Portals uses this entity to allow subscription to Service Requests.
Subscribing to a Service Request
On the Service Request Details page, you can subscribe to a Service Request in order to receive updates about that service request. To do so just click on the Subscribe button.
When a user subscribes to a Service Request, or any other entity that has alerts enabled, this creates an Alert Subscription record in the CRM that is related (via the standard "regarding" relationship on all activity entities) to the item the user subscribed to.
When a change is made to the related record, it is up to a workflow to send an Email and/or SMS message to all subscribers. The ForEach Workflow Helper is used to iterate through all Alert Subscription records related to the updated record and send the alert for each one.