Feed::Parser::NS::Aggregation -- The RSS Aggregation module
Provides aggregator-added information about the original source of the RSS
item.
xmlns:ag="http://purl.org/rss/1.0/modules/aggregation/"
OR
xmlns:ag="http://purl.org/rss/modules/aggregation/"
The former seems to be the official value however the second shows up in the examples provided in the specification.
Specified in: http://web.resource.org/rss/1.0/modules/aggregation/