  Dynamic Epistemic Logic (DEL) provides a framework for epistemic planning
that is capable of representing non-deterministic actions, partial
observability, higher-order knowledge and both factual and epistemic change.
The high expressivity of DEL challenges existing epistemic planners, which
typically can handle only restricted fragments of the whole framework. The goal
of this work is to push the envelop of practical DEL planning, ultimately
aiming for epistemic planners to be able to deal with the full range of
features offered by DEL. Towards this goal, we question the traditional
semantics of DEL, defined in terms on Kripke models. In particular, we propose
an equivalent semantics defined using, as main building block, so-called
possibilities: non well-founded objects representing both factual properties of
the world, and what agents consider to be possible. We call the resulting
framework DELPHIC. We argue that DELPHIC indeed provides a more compact
representation of epistemic states. To substantiate this claim, we implement
both approaches in ASP and we set up an experimental evaluation to compare
DELPHIC with the traditional, Kripke-based approach. The evaluation confirms
that DELPHIC outperforms the traditional approach in space and time.
