  We introduce forest straight-line programs (FSLPs) as a compressed
representation of unranked ordered node-labelled trees. FSLPs are based on the
operations of forest algebra and generalize tree straight-line programs. We
compare the succinctness of FSLPs with two other compression schemes for
unranked trees: top dags and tree straight-line programs of first-child/next
sibling encodings. Efficient translations between these formalisms are
provided. Finally, we show that equality of unranked trees in the setting where
certain symbols are associative or commutative can be tested in polynomial
time. This generalizes previous results for testing isomorphism of compressed
unordered ranked trees.
