squared error loss (f (x) − y) 2 .
the task of active learning is then to find a set of points 1 While in practice it may be sufficient to optimise a given model, and therefore mould a corpus using AL to fit it, this loses sight of the bigger aim, that of studying phenomena for understanding how something works; further, it has been shown to even be detrimental in some cases to apply data acquired for one model using AL to another model (Baldridge, 2004;Rubens and Sugiyama, 2006;Sugiyama and Rubens, 2008 to label X L as to minimize the expected prediction error: in our settings the task is unknown, i.e.