2. Handling simultaneous cofunctions

Co-productions and co-processings are cofunctions that occur at the same time and can therefore be analyzed at the level of a given elementary process: these are known as simultaneous cofunctions. In this section, we present various methods for solving problems involving assignments to cofunctions fulfilled at the same time. These include co-productions, co-processing and revaluations, seen as simultaneous cofunctions. A first strategy is to modify the system under analysis: either by a detailed study of the processes followed by a breakdown of the system, or by an extension to other systems fulfilling the same functions. A second method is to establish allocation rules based on physical and/or socio-economic indicators. Most authors combine several methods.

The first step common to all these methods is to define the system under study (boundaries, incoming and...