As discussed by Robin Torrence (1986: 5), exchange is not directly observable but requires interpretation of the evidence found in consumption sites and in the initial procurement and production areas for artifacts.

Figure 2-4. Model for inference about prehistoric exchange (from Torrence 1986: 5).

Seldom does the act of exchange leave direct evidence of having occurred in a particular location, and the activity must be inferred from the circumstances surrounding production, exchange, and consumption of the product. Note that "Acquisition" (Figure 2-4), or the source area for a product, links directly to all other modes except discard and re-use. In other words, as observed by Torrence, quarry areas are in a unique position for investigating a complete exchange system because it is only "Acquisition" at the quarry area that articulates in some form with most of the major nodes in the Figure 2-4 conceptual model.

When archaeologists encounter non-local materials in their studies, there are commonly three alternative interpretations for this evidence of contact: (1) migration, (2) trade or exchange, (3) conquest by a non-local group. Differentiating these forms of contact from archaeological consumption data can be difficult, and a larger view of the context of exchange is required.

In the 1970s when exchange studies were being widely discussed by archaeologists, two principal approaches were adopted: (1) The system-level view, presented by Renfrew and his associates (1969;1972;1975), and, (2) the political or social view of trade relations (Adams 1974;Friedman and Rowlands 1978;Kohl 1975;Tourtellot and Sabloff 1972) that became more prominent in the 1980s. The systems-oriented approach integrates data into a comprehensive framework, but it is weakened by gradualistic and adaptationist underpinnings as it is

...assumed to have a smoothly, internal inevitability of its own... however it is absurd to think of this as the path that at least the more complex societies have normally followed. They dominate the weaker neighbors, coalesce, suffer themselves from varying forms and degrees of predation, develop and break off patterns of symbiosis - all in dizzyingly abrupt shifts (Adams 1974: 249).

As more recent, agent-centered analyses argue, exchange is a dimension of society that is particularly susceptible to the ambitions of entrepreneurs or aspiring elites because expressions of non-local association and alliance are one manner in which social differentiation can be achieved (Appadurai 1986:38;Clark and Blake 1994;Wiessner 2002: 233).