Activity Streams is an open format specification for activity stream protocols, which are used to syndicate activities taken in social web applications and services, similar to those in Facebook's, Instagram's, and Twitter's. The standard provides a general way to represent activities.
Providers are various services that resolve CURIEs to URLs. The example CURIE
ac:Add is used to demonstrate the provides available for
ac. Generation of OLS and BioPortal URLs requires additional programmatic
logic beyond string formatting.