  In Knowledge Representation, it is crucial that knowledge engineers have a
good understanding of the formal expressions that they write. What formal
expressions state intuitively about the domain of discourse is studied in the
theory of the informal semantics of a logic. In this paper we study the
informal semantics of Answer Set Programming. The roots of answer set
programming lie in the language of Extended Logic Programming, which was
introduced initially as an epistemic logic for default and autoepistemic
reasoning. In 1999, the seminal papers on answer set programming proposed to
use this logic for a different purpose, namely, to model and solve search
problems. Currently, the language is used primarily in this new role. However,
the original epistemic intuitions lose their explanatory relevance in this new
context. How answer set programs are connected to the specifications of
problems they model is more easily explained in a classical Tarskian semantics,
in which models correspond to possible worlds, rather than to belief states of
an epistemic agent. In this paper, we develop a new theory of the informal
semantics of answer set programming, which is formulated in the Tarskian
setting and based on Frege's compositionality principle. It differs
substantially from the earlier epistemic theory of informal semantics,
providing a different view on the meaning of the connectives in answer set
programming and on its relation to other logics, in particular classical logic.
