Realizing public announcements by justifications

• We study two dynamic epistemic logics with justifications.
• We prove a realization theorem for the modal logic of public announcements.
• We develop a realization method by translation.

Modal public announcement logics study how beliefs change after public announcements. However, these logics cannot express the reason for a new belief. Justification logics fill this gap since they can formally represent evidence and justifications for an agent's belief. We present OPAL(K)OPAL(K) and JPAL(K)JPAL(K), two alternative justification counterparts of Gerbrandy–Groeneveld's public announcement logic PAL(K)PAL(K). We show that PAL(K)PAL(K) is the forgetful projection of both OPAL(K)OPAL(K) and JPAL(K)JPAL(K). We also establish that JPAL(K)JPAL(K) partially realizes PAL(K)PAL(K). The question whether a similar result holds for OPAL(K)OPAL(K) is still open.