Andrew and Don, this is a brilliant research breakthrough. I hope you'll be presenting it at Extreme this year!

I did notice two areas in which you might seek further improvements:

First, drag can be radically reduced by avoiding discontinuities in the cross-sections of successive slices. That is, the contours of the message should not be irregular from front to back. Thus, attending to the contours of the enclosed text would help greatly. For example, instead of

it would be much more efficient to achieve laminar flow over nearly the entire stream by transmitting:

Second, recent research in the High-Speed Undersea Weapons Project (see http://www.onr.navy.mil/sci_tech/engineering/333_mechanics/usea_highspeed.asp) shows that at sufficient speeds, a properly-shaped projectile can create a cavitation bubble entirely surrounding itself. Above that critical speed, it is actually travelling in a gaseous space even while submerged in a liquid (cool picture at http://www.supercavitation.com/html/message_board.html). This reduces drag by about 1000x, and was first demonstrated with the Russian VA-111 Shkval torpedo, which operates at more than 230mph.

The optimal shape for supercavitation is a flat, sharp-edged nose. The XML "<" is thus ideal. However, it is clear that supercavitating two-phase flows are not achieved for XML transmissions in practice. It is likely that the reason for this is that the present Internet is incapable of accelerating XML data to the minimum velocity required, about 100mph.

Should this general Internet limitation be overcome, XML documents should naturally begin to supercavitate, making them nearly 1,000 times more efficient than other documents.

Thanks again, Andrew and Don, for opening up a very promising new area of XML research!

Steve DeRose

At 10:56 -0700 2005-04-06, Andrew Layman wrote: