Many of the ontology proposals are based on the assumption
that everybody is going to magically convert overnight to
whatever new standard is proposed. (01)
However, there are still legacy software systems running
today that were written over 40 years ago. The only reason
why there aren't many that are older is that computers only
became widely available in the 1960s. (02)
There's an article about the final days of Edison's original
direct-current service in New York City: (03)
http://cityroom.blogs.nytimes.com/2007/11/14/off-goes-the-power-current-started-by-thomas-edison/
Off Goes the Power Current Started by Thomas Edison (04)
But the shut-down of DC service does not mean that the old
equipment will be shut down. Instead, they're using converters
from AC to DC: (05)
> The last snip of Con Ed’s direct current system will take place
> at 10 East 40th Street, near the Mid-Manhattan Library. That
> building, like the thousands of other direct current users
> that have been transitioned over the last several years, now
> has a converter installed on the premises that can take
> alternating electricity from the Con Ed power grid and adapt
> it on premises. (06)
In 1928, they predicted that it would take 45 years to convert
all the DC equipment. But the equipment is still running today,
even though the service has been terminated. (07)
This provides some perspective on interoperability: any new
proposal must be able to accommodate legacy systems, and it
must be designed with the knowledge that the new system will
also become a legacy. (08)
John Sowa (09)
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