Time plays a particular role in defining the relevant market. A market can exist only for a specified period of time, in the absence of substitutability of products or services offered during that period. According to the EU judicature, the finding of the existence of a dominant position results from an analysis of the structure of the market and the competition prevailing on it at the time of the adoption by the Commission of each decision. The definition of the market may then vary over time, as the characteristics of the products and services evolve and the possibilities of substitution, particularly on the demand side, change. The determination of the relevant market, which is not static, may therefore, as the case may be, reflect technological developments, irrespective of the definitions previously adopted by the various authorities.