  The purpose of this paper is to revisit the Panko-Halverson taxonomy of
spreadsheet errors and suggest revisions. There are several reasons for doing
so: First, the taxonomy has been widely used. Therefore, it should have
scrutiny; Second, the taxonomy has not been widely available in its original
form and most users refer to secondary sources. Consequently, they often equate
the taxonomy with the simplified extracts used in particular experiments or
field studies; Third, perhaps as a consequence, most users use only a fraction
of the taxonomy. In particular, they tend not to use the taxonomy's life-cycle
dimension; Fourth, the taxonomy has been tested against spreadsheets in
experiments and spreadsheets in operational use. It is time to review how it
has fared in these tests; Fifth, the taxonomy was based on the types of
spreadsheet errors that were known to the authors in the mid-1990s. Subsequent
experience has shown that the taxonomy needs to be extended for situations
beyond those original experiences; Sixth, the omission category in the taxonomy
has proven to be too narrow. Although this paper will focus on the
Panko-Halverson taxonomy, this does not mean that that it is the only possible
error taxonomy or even the best error taxonomy.
