The theme of mendicancy has been treated by various authors throughout the twentieth century, normally in discussions on poverty and the gift. The case of many groups of Sinti and Rom in Western Europe demonstrates how conventional economic categories can be dismantled and reassembled within different contexts of meaning. The sequence of the act of beggary only partially corresponds to that of the gift in Mauss's theory, and thus that theory is only marginally applicable to it. The most important element of Gypsy begging to consider is that it is based on a "relationship value" (typical of gifts) which tends to be non-existent, thereby maintaining a capacity for exiting from interpersonal interaction similar to that of commercial transaction. It is for this reason that some Gypsy groups do not distinguish begging from trade in their terminology, and it is through this activity, too - often unconnected to a condition of poverty - that they have historically constructed what has been called their "subversive economy".