The third annual RoboCup, a 10-day event officially described as the robot world cup soccer tournament, is starting in the Swedish capital Stockholm.

Ninety teams from 20 countries are to compete in a series of football matches in various classes according to the size and intellectual capacity of the automaton.

Some are about the size of a teacup, others that of a small waste bin and there is even a canine class featuring the robotic dogs that have proven so popular as virtual pets in Japan.

And in the virtual class itself, of course, the robots will not exist at all except in cyberspace.

The individual real robots, so to speak, are controlled by computer- linked cameras which transmit instructions according to the state of play, with no human intervention.

In the larger classes the cameras are incorporated within the robots, which are pre-programmed to react to the ball and communicate with each other.

Enthusiasts are confident that a humanoid league will be competing by 2003 although truly human World Cup standards of play are probably at least 50 years away.

The serious side of RoboCup is reflected in the fact that the 16th international joint conference on artificial intelligence - a biennial event - is taking place concurrently in Stockholm.