As soon as the Subscription Backport Guide is published and R4B named by regulations, the intent to update this guide to support the task based subscriptions framework.  Since these dates are currently unknown we cannot project when those changes will be made.  After that we anticipate broader adoption and support  of  subscriptions.   Will update the STU Note to document the intent to update subscription once the  milestones are met. This project recognizes the major revisions to the reworked R5 subscription "topic-based" pub/sub pattern and the future publication of a Subscription R5 Backport Implementation Guide for FHIR 4 and recent publication of [FHIR4B] ( http://hl7.org/fhir/r4b-explanation.html ) to address the many shortcomings in the current (R4) approach to subscriptions. Due to these imminent changes in the FHIR pub/sub pattern, the discovery process for subscription support is out of scope for this version of the guide. The Payer may discover it out-of-band or simply through trial-and-error. As soon as the Subscription Backport Guide is published and R4B named by regulations, the intent to update this guide to support the task based subscriptions framework.   Re: Polling.  Added this paragraph ( adapted form HREX and PAS IGs): Data consumers can poll for a single Task or across several Tasks. The frequency needs to be often enough that the time between when the relevant data is created and when the Data Consumer receives it is sufficiently short for the Data Consumer's needs. However, it needs to be infrequent enough that the data source's resources are not over-taxed by the repeated query. Data Consumers { }SHOULD{ } perform this operation in an automated/background manner no more than every 5 minutes for the first 30 minutes and no more frequently than once every hour after that.