>>>Using Oracle would defeat the aim of having a small and more or less self-contained application + data. What commonly using applications have the longest lived backwards compatibility? Excel? RTF word processors?
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>>Stuff written in Cobol and Fortran.
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>For sure. But most of that has another advantage in that it is mostly IBM-based and IBM learned its lesson in the early 1960s when it FORCED all current users to re-write everything that had been written for the 1400-series (and 7000-series, for the few who had them). Their user base threatened en-masse to go elsewhere and IBM promised to never do that again. To my knowledge, they have kept their word.
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>I see the problem here as quite different. In the "PC" (as opposed to 'mainframe') world we have unrelated hardware vendors, software vendors and application writers as well as 'supplies' (diskettes, tapes, etc) manufacturers.
>COM ports seem to be going fast. Parallel ports even faster? I have a hard time finding replacement RAM for my older PC. Seen any 5 1/2 inch diskettes for sale recently? Windows 95, Windows 98 and even Win XP SP1 are no longer supported.
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>I honestly think it is foolhardy for anyone to think they can either continue to run, or resurrect in 30 years, an application written today! The pace of change is growing daily and consideratons for the past are shrinking.

There are only few M$ apps which are (sufficiently) compatible with what they were 10 or 15 years ago - Notepad, Solitaire and Fox :).