Saturday, December 31, 2005

Spreadsheets: dangerous to your organization?

Most of us use spreadsheets regularly. Indeed, starting with Visicalc, spreadsheets have been a major convenience factor for personal computers of all sorts, enabling non-programmers (or programmers who want an easier way) to make valuable calculations.

For some time, I've been worried about spreadsheets. For example, I've noted that it's far too easy to enter a value in a cell, overwriting a formula, and then forgetting to set it back to the formula. I've seen such errors get discovered weeks or months later when, for example, faulty but hoped-for financial projections in a spreadsheet don't come true.

Comp.risks posted potentially valuable links to sites that discuss errors in spreadsheets, and their work seems to validate my suspicions. Hardwiring, that overwriting of a formula by a constant, is "very common," although its incidence can be eliminated by protecting all cells with formulas. (No, I don't always do that, either.)

If you're so inclined, check out the research, and consider how you can insure the spreadsheets in your organization won't lead you astray. Consider best practices they suggest.

For even better security, I might suggest beginning to move to an array programming language, in which the calculations and the data are clearly separate and can be examined separately and easily. J is one such language; its tacit expressions can provide an easy path to a personal, custom calculator that can provide you the data you want and that is quite insusceptible to hardwiring errors. Check out Easy J for a quick introduction.

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