In New York, you must be a registered Democrat or Republican to vote in the primary election; a portion of the 16 percent from that district might not know that. New Yorkers registered with a third party, such as the Green Party, Independence Party, Libertarian Party or Working Families Party, can't vote in the primary.
Collaborative filtering (CF) is a method used by some recommender systems. It consists of two senses, a narrow one and a more general one. In general, collaborative filtering is the process of filtering for information or patterns using techniques involving collaboration among multiple agents, viewpoints, data sources.
Online collaboration platforms is a general catch all term to describe a range of internet based tools that allow people to do things together online. This may include online conversations in forums and email lists, co-creation of documents on wikis, file sharing and storing, etc.