Question: which subclass of information filtering system was work of John Thomas Riedl

Context paragraphs:
Thomas Riedl: Thomas Riedl (born 18 June 1976 in Kaiserslautern) is a German former footballer.  He is the son of Hannes Riedl, who played for 1.  FC Kaiserslautern in the 1970s.

Psychographic filtering: Psychographic filtering is located within a branch of collaborative filtering (user-based) which anticipates preferences based upon information received from a statistical survey, a questionnaire, or other forms of social research.  The term "Psychographic" is derived from Psychography which is the study of associating and classifying people according to their psychological characteristics.  In marketing or social research, information received from a participant’s response is compared with other participants’ responses and the comparison of that research is designed to predict preferences based upon similarities or differences in perception.  The participant should be inclined to share perceptions with people who have similar preferences.  Suggestions are then provided to the participant based on their predicted preferences.  Psychographic filtering differs from collaborative filtering in that it classifies similar people into a specific psychographic profile where predictions of preferences are based upon that psychographic profile type.  Examples of psychological characteristics which determine a psychographic profile are personality, lifestyle, value system, behavior, experience and attitude.

Joseph A. Konstan: Joseph A. Konstan is an American computer scientist, the Distinguished McKnight University Professor and Distinguished University Teaching Professor at the University of Minnesota.  His research interests are human computer interaction, social computing, collaborative information filtering, online communities and medical and health applications of Internet technology.  He is best known for his work in collaborative filtering recommenders (the GroupLens project), and for his work in online HIV prevention.

John T. Riedl: John Thomas Riedl (January 16, 1962 – July 15, 2013) was an American computer scientist and the McKnight Distinguished Professor at the University of Minnesota.  His published works include highly influential research on the social web, recommendation systems, and collaborative systems.

Internet censorship in New Zealand: Internet censorship in New Zealand refers to filtering website traffic to prevent Internet users in New Zealand from accessing certain selected sites and material, specifically material that deals with the sexual abuse or exploitation of children and young persons.  The Department of Internal Affairs runs the filtering system.  It is voluntary for ISPs to join.

Information filtering system: An information filtering system is a system that removes redundant or unwanted information from an information stream using (semi)automated or computerized methods prior to presentation to a human user.  Its main goal is the management of the information overload and increment of the semantic signal-to-noise ratio.  To do this the user's profile is compared to some reference characteristics.  These characteristics may originate from the information item (the content-based approach) or the user's social environment (the collaborative filtering approach).

Collaborative filtering: In the newer, narrower sense, collaborative filtering is a method of making automatic predictions (filtering) about the interests of a user by collecting preferences or taste information from many users (collaborating).  The underlying assumption of the collaborative filtering approach is that if a person "A" has the same opinion as a person "B" on an issue, A is more likely to have B's opinion on a different issue than that of a randomly chosen person.  For example, a collaborative filtering recommendation system for television tastes could make predictions about which television show a user should like given a partial list of that user's tastes (likes or dislikes).  Note that these predictions are specific to the user, but use information gleaned from many users.  This differs from the simpler approach of giving an average (non-specific) score for each item of interest, for example based on its number of votes.

Recommender system: A recommender system or a recommendation system (sometimes replacing "system" with a synonym such as platform or engine) is a subclass of information filtering system that seeks to predict the "rating" or "preference" that a user would give to an item.

Johannes Riedl: Johannes Riedl (born 2 January 1950 in Pirmasens; died 19 August 2010) was a German football player.  He played 441 games in the Bundesliga.  He is the father of Thomas Riedl.

Internet in Bahrain: Bahrain has been connected to the internet since 1995, and made it readily available to its citizens.  The country's domain suffix is '. bh'.  A 2004 study showed a liberal filtering system is used in Bahrain, one which can be easily bypassed, however more recent events have shown more sophisticated and pervasive filtering.  In January 2009, Bahrain has started blocking a vastly increased number of sites through the Information Affairs Authority (IAA).  The new filtering has had a noticeable impact in internet access speeds for all traffic.

Supporting paragraphs: John T. Riedl Recommender system
Answer: A recommender system