The present

Have you ever wondered how many different data people have to know to communicate with you? Some time ago people used to live in small villages and then everybody knew each other and it was enough for them to know the house where you live and they could easily get there and talk with you. But then transports improved and people started to travel long distances and become interlaced with people from distant places. Then you could not just give people such indications as "I live in the red-brick house in front of the gourcery of the main street": you had to give more precise information. It was then that the postal system was developed, with is street numbers, its postal codes and so on. And then people had to know several names and numbers whenever they wanted to get in touch with you.

Some time later, a great leap forward in communications was introduced: the telephone. But unfortunately it happened that your postal address was not quite the right way to find you at the other side of this marvelous machine. Telephone numbers were introduced and, if you wanted people to talk to you, you had to give them this long series of numbers. Yet most people used to be at different places at different times of the day, so more than a single telephone number was needed. But telephones were only a small step in the great communications revolution. Not a long time ago, mobile telephony arrived, and then we had to add another telephone number to the list we had. And some time later, intenet popularized and we started to use emails and the web. Then people had to know even more data to communicate with you. But why, you may ask? If I'm always the same and only the channel is different, why do they have to use every time a differente set of information, a different address to communicate with me?

Of course, the ammount of information was so big that nobody was able to remember all these data so they found a reasonable solution which they called agenda. This was however, to say the best, a wrong solution. This is because it was based on redundancy. If you have, let us say, one hundred friends, relatives and coworkers, then everyone of them has to have the same information about you, saved in their agendas (mostly electronic ones). And then every time you have to change a small bit of your information (for example because you moved for three months to another town), you have to tell them all (supposing you have their addresses up to date) to change this small piece of information in the agendas. Not quite practical in the era of electronic communications and the internet.