Entity data represent entities related according to a hierarchy, with at least one root entity at a highest level and one or more entities at one or more levels below the highest level. One or more entities each have multiple instances, and at least one attribute having respective elements for each of the instances. Input data includes expressions that express functions of arguments, with one or more of the arguments referencing an attribute of an entity represented in the entity data. Processing expressions includes: (a) analyzing an expression to determine, for each of one or more attributes, at least one of: (1) a position in the hierarchy of an entity of the attribute, or (2) a number of elements of a result of a function applied to an argument that references the attribute, and (b) evaluating the expression, or indicating an error based on a result of analyzing the expression.