Audi has confirmed that production of its new Mini rival, the much-anticipated A1, will begin in 2009. New Audi CEO Rupert Stadler also confirmed this week that the forthcoming premium supermini will be built at Volkswagen's Brussels plant, and that the firm is projecting to produce 100,000 units per year - roughly half the number of Minis that BMW make.The A1 will play a bit part in Audi's expansion plans. Last year the German company made 900,000 units; in 2015, it plans to make 1,500,000, and making the A1 a success will be crucial to hitting that target. However, it must also be a profitable car for Audi; the last time Ingolstadt entered the supermini market, it did so with the all-aluminium A2, which cost too much both to develop and to build.The A1 will be different. Audi has yet to release any official information about the car's mechanicals, and industry commentators are divided on which platform it's likely to use to form the basis of the car.Autocar's sources suggest, as we reported back in 2005, that the new car will be based on a version of the same mechanical structure that underpins the new generation of VW's Polo supermini family (the VW Polo, Skoda Fabia and Seat Ibiza).The platform's codename is 'PQ25', and it has been developed by the VW group in order to accomodate four-wheel drive, with the A1 in mind. Company insiders suggest that Audi will modify the platform with lighter, more sophisticated chassis componentry, but beyond that will keep tweaks to minimum in order to keep costs down.Like the Mini, the car will be a three-door only, leaving room for a slightly taller, five-door 'A2' variant above it to come later on in the car's lifecycle. Prices for it are likely to start around £12,000. Owners will therefore be expected to pay a premium of around £3k over an equivalent VW Polo for the A1. The success of BMW's Mini suggests that the market will support that kind of premium, but only for the right product, and Audiphiles should get a first look at that product when the firm previews it, with a forward-looking supermini concept, at this year's Frankfurt motor show.