Methods, computer program products, and systems are presented. The method, computer program products, and systems can include, for instance: initiating evaluating of a tree data structure expression having nodes and edges between the nodes, wherein a plurality of nodes of the tree data structure expression express functions, and wherein a hierarchy of the tree data structure expression defines an order of execution of functions expressed by nodes of the plurality of nodes; and in response to the initiating, reading, processing and writing tile data of a dataset according to node expressed functions of the tree data structure expression.