> pundits on both the "it will collapse under demand" and the
> "bandwidth will keep being added" sides.

I went to a workshop yesterday on high performance protocols, where
one of the topics was what benefit you could get from a really fast
network link. Using 25Mbit/sec ATM (asynchronous transfer mode) an
X.400 system managed only 10,000 messages of 7Kb per hour while a
system using internet protocols managed over 60,000.

However it would be an oversimplification to just say, `well X400 is
a phone company protocol. Don't you expect it to chew bandwidth?'
There are bottlenecks sending all the control signals back and forth
between the user and message transfer agents. Simply adding bandwidth
won't necessarily help you much.

> I think the more interesting point you make, though, is on the signing
> of clinical messages:  Whilst I fully understand the need for this in
> the mesaging/EDI paradigm, it is much less clear to me whether such
> signatures are a necessity/relevant in the Web/interactive paradigm

A few days ago, I had to send a fax to a crypto company in America. I
hit their web page, cut and pasted the mail and fax addresses into
the letter, and shipped it. Eventually I got email asking where the
fax was. It turned out that the contact data I had fetched from what
appeared to be their site had been completely wrong. They are now
looking at whether it was an attack on them.

Fortunately the letter's contents were not at all sensitive.

> the path results are not physically copied via EDI from hospital
> system to GP system but are accessed interactively each time they are
> needed

This is not entirely clear. US hospitals, who keep everything, are
now accumulating digital image data at a rate of about 1TB per
hospital per year. That costs money to store. In the NHS, as you
know, films get recycled and disk space gets reused.

So it may well be prudent for a physician who is making a critical
diagnosis on the basis of a medical image to cache a copy of it with
the patient's record, for both clinical and medico-legal reasons.

Ross


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