 If the domains needed for an adequate definition of sequentiality are to describe the causality relations among occurrences of computational events, then it is necessary to enrich our picture by considering events as located at places, generalizing the notion of argument place in the definitions of Vuillemin and Milner which depends on how a function is presented. This led to a notion of concrete data structure (cds) (Kahn &amp; Plotkin 1993) and to an axiomatization of the order-theoretic properties of domains of first-order data. Kahn and Plotkin obtained a representation theorem for the domains described by their axioms, the concrete domains, in terms of the states of a process of exploration of a concrete data structure that consists in filling, given a state \(x\), any cell enabled by sets of events that have already happened in \(x\), starting from initial cells enabled in the initial, empty state: this is similar to proving theorems in an abstract deductive system whose rules are the enablings. As a motivating example, think of a linked list of, say, natural numbers. The initial cell may be filled at any time with any value \(n_1\). This event enables the second cell of the list, which may then (and only then) be filled with any value \(n_2\), and so on for all later cells.