1. A method of operating a computing device to execute a document authoring tool that forms an interactive document, the method comprising: with at least one processor: receiving a plurality of user inputs defining elements of the interactive document, the elements comprising: a plurality of entities to be incorporated in the interactive document; a transformation indicating a relationship between input data and output data of a first entity of the plurality of entities; a visualization for visually representing input data of a second entity of the plurality of entities, wherein the document authoring tool selects a visualization with interactivity and represents the visualization with interactivity by a third entity and a fourth entity, the third entity comprising an entity with an input and no output and the fourth entity comprising an entity with an output and no input, wherein the third entity is separate and disconnected from the fourth entity; and a plurality of edges, each of the plurality of edges indicating a data flow between two of the plurality of entities; and verifying that the plurality of edges interconnect the plurality of entities in an acyclic graph, wherein the plurality of entities are of a plurality of types.