A system handles conditional dependencies between alternative product segments of a production process modeled within a manufacturing execution system (MES). The system includes data processing units connected to a network and production components. The data processing units run MES software for controlling and monitoring the process. The MES software includes a production modeler embedding time-sensitive dependency information in each product segment to define the start of execution in relation to another product segment. The production modeler embeds in each product segment programmed for alternative execution conditional dependency information and a sequence attribute about the order of evaluation of the specified condition. The MES software, during execution of a product segment preceding alternative executions, checks the condition specified as first in the set of sequence attributes and, if that condition is satisfied, executes the product segment corresponding with that condition, otherwise iterates the check for execution until a condition is satisfied.