One area that has received particular attention is the effort to understand computational mechanisms. On some accounts, computational mechanisms form a proper subclass of mechanisms that can be defined explicitly in terms of the kinds of entities, properties, and activities involved in mechanisms in that class (Piccinini 2007; Milkowski 2013). According to this view, computational mechanisms are mechanisms that have the function to manipulate medium independent vehicles in accordance with a general rule that applies to all vehicles and depends on the inputs for its application (Piccinini and Scarantino 2011). Digital computers are distinctive in that their vehicles are digits (Piccinini 2007). Proponents of this account hope to demarcate computing mechanisms from non-computing mechanisms by appeal to the distinctive components proprietary to computing mechanisms. This view contrasts both with a semantic view, according to which computation is essentially a matter of manipulating symbols or representations, and with perspectivalist views, according to which whether a mechanism counts as computing is a matter of whether it is so described (Churchland 1986; Churchland and Sejnowski 1992; Shagrir 2010).