Per default, the field for the activity link is left empty by the data provider (i.e. no direct link is used) and the database service layer will then automatically link to the appropriate local market for the specific product and geography, or to the global market if no local markets exist.
Direct activity links are used if the intermediate product of a certain supplying activity is directly used as input. This is necessary when the production volumes of a specific suppliers fluctuates with the demand of the specific customers, so that the product does not come from the average market but directly from that specific supplier. The activity link allows to specify a distinct producing technology as source of the product. When transforming activities are linked directly, thus avoiding the market activities, the activities and data that is normally included in market activities need to be added directly to the activity requiring the input. This includes transport activities, production losses, wholesaler and retailer activities, and product taxes and subsidies for the directly linked input.