Editing Lotus Improv (section)

===ATG===
Lotus set up an advanced technology group in 1986.{{sfn|Garfinkel|1991|p=34}}  One of their initial tasks was to see if they could simplify the task of setting up a spreadsheet. Completed spreadsheets were easy to use, but many users found it difficult to imagine what the sheet needed to look like in order to get started creating it. Should data be entered down columns, or across rows? Should intermediate values be stored within the sheet, or on a separate one? How much room will we need?{{sfn|Garfinkel|1991|p=34}}

[[Pito Salas]], a developer at ATG, decided to attack this problem.<ref group=N>Garfinkel and Jelen appear to disagree on Salas' role in ATG. Garfinkel implies that he simply worked at ATG, while Jelen seems to imply he set it up. See Garfinkel, p. 34 and Jelen, p. 28.</ref> After a few months of studying existing real-world examples, it became clear that the data, views of that data, and the formulas that acted on that data were very separate concepts. Yet in every case, the existing spreadsheet programs required the user to type all of these items into the same (typically single) sheet's cells.

This overlap of functionality led to considerable confusion, because it's not obvious which cells hold what sort of data. Is this cell an input value that is used elsewhere? Is it an intermediate value used for a calculation? Perhaps it is an output value from a calculation? There's no way to know. This insight led to ideas for a new spreadsheet that would cleanly separate these concepts &mdash; data, formulas, and output views that would combine data and formulas in a format suitable for the end user. At the same time, the new product would allow users to group data "by purpose", giving it a name instead of referring to it by its position in the sheet. This meant that moving the data on the sheet would have no effect on calculation.{{sfn|Garfinkel|1991|p=34}}

Salas also noted that it was the views of output data that was often the weakest part of existing spreadsheets. Since the input, calculations and output were all mixed on a sheet, changing the layout could lead to serious problems if data moved. With the data and formulas separated, this was no longer an issue. Salas demonstrated that this separation meant that a number of common tasks that required lengthy calculations on existing spreadsheets could be handled almost for free simply by changing the view. For instance, if a spreadsheet contained a list of monthly sales, it was not uncommon to have an output column that summed up the sales by month. But if one wanted that summed by year, this would normally require another formula column and a different output sheet.{{sfn|Garfinkel|1991|p=34}}