Grandmothers and designers' expectations

Bruce MacIsaac:

Systems often outlive the assumptions of their original designers. The millenium bug is a classic example. Assuming that the software would be replaced by 1999, early designers used two-digit dates. That assumption cost billions to correct. My own grandmother was the victim of a similar false assumption. When my grandfather passed away in the 1970s, she bought a dual headstone, precarved with her name and "19__". At the age of 112, Mary MacIssac, like many legacy systems, continues to outlive the designer's expectations.
From the Leverage Legacy Systems chapter of Agility and Discipline Made Easy. Practices from OpenUP and RUP (amazon.com,amazon.co.uk ,safari), by Per Kroll and Bruce MacIsaac.

Bruce dedicates the book to his grandmother.