The limitations of backpropagation learning can now be overcome by using multilayer neural networks that contain top-down connections and training them to /generate/ sensory data rather than to classify it. (...) much better than previous approaches
In computer science, a kd-tree (short for k-dimensional tree) is a space-partitioning data structure for organizing points in a k-dimensional space. kd-trees are a useful data structure for several applications, such as searches involving a multidimensional search key (e.g. range searches and nearest neighbour searches).