Hashtags Access Control and Notifications
Aside from being beneficial from a visualization and analytical perspective, Hashtags can be used to control what Users can see when they log-in to Opsview Monitor.
This means you can navigate through Configuration > Hosts and Configuration > Service Checks, tag those objects with your Hashtag, and then create a Role that gives Users access to only view/configure objects tagged with the given Hashtag.
For information on how to configure Roles, view Roles.
For those Users in the newly created Role, you can then create and assign a shared notification profile that only notifies them when a problem occurs on objects tagged with the given Hashtag.