Issue 80325

Unlike tracking changes in text documents, tracking changes in spreadsheets is
substantially different.

This is part of the more general issue 80139. This is partially an extension of
issue 28386 (see http://www.openoffice.org/issues/show_bug.cgi?id=28386).

TOC
===
1. Functional Units
2. Changes in Computed Values
3. Tracing Back Changes

1. Functional Units
===================
In a spreadsheet we are usually interested to track changes in some calculated
output. I am not very interested in individual changes.

Rather, the spreadsheet should be split into *functional units* and one should
be able to track only changes in that specific unit. The functional units are a
more advanced concept of issue 28386.

This is especially useful for complex spreadsheets and in cases where many users
work on the spreadsheet. The users are interested only in overviewing a specific
part of the spreadsheet.

2. Computed Values
==================
The Calc track-changes system is currently not able to sense changes in a
computed value.

Lets say, we have in cell C1=SUM(A1:B1) and one user changes the value in cell
A1. Now, A1 is marked as changed, BUT cell C1 is NOT marked. However, most users
will be interested in the *downstream effect* that the initial change had.
Therefore, Calc should be able to track changes even in computed values.

3. Trace Back
=============
Once point (2) is implemented, one may find a downstream (computed) value that
looks suspect. In that case the user surely wishes to trace back the changes in
an upstream value that produced this suspect computation.

Most often - when I overview a spreadsheet that is updated by many workers - I
wish to check only some downstream values (computed summaries). You will never
have time in such a complex environment to check everything, so one is limited
to checking the results.

If I detect an unnatural result, I wish to be able to check the upstream changes
that resulted in this dubious result, and check if those changes/new values were
correct.