1. A computer system for building down a mathematical expression, the application comprising: a processor; and a computer-readable storage medium encoding instructions that, when executed by the processor, cause the application to: create an input module programmed to accept input of a sequence of characters of the mathematical expression; create a builddown module programmed to receive a request to builddown all of the sequence of characters of the entire mathematical expression from a two-dimensional format to a linear format, the builddown module being configured to accept the request to builddown from both a user to builddown the mathematical expression in a first document and an automated global builddown request to builddown all of a plurality of mathematical expressions, including the mathematical expression, in the first document and at least one document other than the first document, the linear format of the mathematical expression including all of the sequence of characters in the linear format, wherein the builddown module is programmed to associate a special property of the two-dimensional format of the entire mathematical expression with a corresponding character of the sequence of characters of the linear format of the entire mathematical expression, wherein the special property is selected from a group consisting of formatting attributes and mathematical attributes, and wherein the special property is associated as a formatting run in a backing store that is stored parallel to a formatting run associated with the corresponding character of the sequence of characters of the linear format; and create a formatting module programmed to format the entire mathematical expression upon building the entire mathematical expression back up from the linear format to the two-dimensional format, wherein the formatting module is programmed to apply the special property to the two-dimensional format.