dlvhex is the name of a prototype application for computing the models of so-called HEX-programs, which are an extension of Answer-Set Programs towards integration of external computation sources.

Motivated by the need to interoperate with a broader set of external computation sources and the observation, that for meta-reasoning in the context of the Semantic Web, no adequate support is available in ASP to date, we extended the dl-program approach to HEX-programs, that is, higher-order logic programs (which accommodate meta-reasoning through higher-order atoms) with external atoms for software interoperability. Intuitively, a higher-order atom allows to quantify values over predicate names, and to freely exchange predicate symbols with constant symbols, like in the rule

C(X) :- subClassOf(D,C), D(X).

An external atom facilitates to determine the truth value of an atom through an external source of computation. For instance, the rule

reached(X) :- &reach[edge,a](X)

computes the predicate reached taking values from the predicate &reach, which computes via &reach[edge, a] all the reachable nodes in the graph edge from node a, delegating this task to an external computation source (e.g., an external deduction system, an execution library, etc.).