Switch off
The problem with digital TV is that, unlike analogue, it has only two states - working or broken. Should I buy a box to improve the signal quality of Channel 5 - which in Norfolk is transmitted on a power of less than 2% of the other channels - I will, no doubt, suffer from picture freezing, sudden loss of sound and other distractions I have seen at the homes of other viewers in the area. Digital TV must be more reliable for 95% of the population to allow analogue switch off. Tony Meacock
tonyandpatmeacock@compuserve.com

Torch it
Since I haven't got a mobile phone, from which appliance would Lucy Kimbell (Feedback, January 31) suggest I construct my identity? Something the same size as a mobile phone, such as a torch, or would my washing machine do the trick? Peter Bendall
bendallpeter@hotmail.com

Clear view
While Walé Azeez (January 24) gives the impression that electronic data interchange (EDI) is expensive, complex and proprietary, correspondents (Feedback, January 31) seem to think XML offers a simple and low-cost solution. Neither view is quite true. EDI is about machine-to-machine business: it used proprietary networks when there was no internet, and devised the EDIFACT, X.12 and Tradacoms syntaxes when there was nothing else.

Now there are alternatives, but do they mean a radical change in the way we do business? The internet is cheaper than the old EDI networks, but that has to be weighed against the difficulty, for smaller businesses, of running a reliable, secure service on a 24/7 basis. And XML? It is a markup language for creating markup languages. You need to define your tags before you can trade, and that's a problem. Many competing "standards" have emerged, stalling user-uptake. Much useful work is being done by ebXML but there's no guarantee that theirs will become the single, de facto standard. Until every application is XML-aware, simply switching to XML brings no benefit at all, which is why established EDI users don't bother. The hard problem of e-business is not technology. It is this: you do business differently to me. Your data is not quite like my data; your processes are not like mine. EDI, XML? Plus ça change.
Richard Griffiths
rgriff@cix.co.uk

Hapless hunt
Fantastic! According to Iain Bruce (The mobile manhunt, January 31), you'll soon be able to play real-time man hunts from your mobile phone. When two players meet, the only thing either will know for certain is that they possess a fairly new, posh and expensive mobile phone. Here's an alternative vision: you are in a crowded high street, pursuing your quarry using your phone. The handset beeps again and then, just as you close in, a hand clasps your shoulder, spins you round, you get punched in the face, then your assailant grabs your phone and legs it. Even better, the assailant only needs to steal one expensive phone then sit down and wait for other hapless victims. What a marvellous triumph of technology over security. Antony Hawkins
a.d.hawkins@sheffield.ac.uk

Kosher pips
The rabbi (Lemons add zest, Science, January 31) is not examining a lemon, but is checking an Etrog, a symbolic citrus fruit used on the Jewish festival of Succot. The etrog must have a full "pip" at the top of the fruit or it is not Kosher. Oliver Lovat
oliverlovat@stoneashdown.org

Helping hand
I use Microsoft because it came bundled with the PC. My customers wanted the results in Microsoft format, so I needed to buy Office. Then my ISP gave me more Microsoft software "free". Being a home worker now after 30-plus years of office support gives me a good appreciation of Jack Schofield's articles, which have helped me at least as much as the help files have. Mike Parslow
mike.parslow@innoman.freeserve.co.uk

Pure fiction
Gary Wilkinson (Working the web, January 31) states that the Arthur C Clarke Award is "organised by the academic Science Fiction Foundation". This is not true. The Science Fiction Foundation is one of three organisations who supportthe Award by providing judges; the other two are the British Science Fiction Association and the Science Museum. The organisation of the Award is independent, as I should know, since I do it. Paul Kincaid
Administrator, Arthur C Clarke Award
clarke@appomattox.demon.co.uk