  Cross-lingual summarization consists of generating a summary in one language
given an input document in a different language, allowing for the dissemination
of relevant content across speakers of other languages. The task is challenging
mainly due to the paucity of cross-lingual datasets and the compounded
difficulty of summarizing and translating. This work presents $\mu$PLAN, an
approach to cross-lingual summarization that uses an intermediate planning step
as a cross-lingual bridge. We formulate the plan as a sequence of entities
capturing the summary's content and the order in which it should be
communicated. Importantly, our plans abstract from surface form: using a
multilingual knowledge base, we align entities to their canonical designation
across languages and generate the summary conditioned on this cross-lingual
bridge and the input. Automatic and human evaluation on the XWikis dataset
(across four language pairs) demonstrates that our planning objective achieves
state-of-the-art performance in terms of informativeness and faithfulness.
Moreover, $\mu$PLAN models improve the zero-shot transfer to new cross-lingual
language pairs compared to baselines without a planning component.
