Published online by Cambridge University Press: 15 March 2005
A Σ-labeled n-poset is an (at most) countable set,labeled in the set Σ, equipped with n partial orders.The collection of all Σ-labeled n-posets is naturallyequipped with n binary product operations andnω-ary product operations.Moreover, the ω-ary product operationsgive rise to nω-power operations.We show that those Σ-labeled n-posets that can be generated fromthe singletons by the binary and ω-aryproduct operations form the free algebra on Σin a variety axiomatizable by an infinite collection of simpleequations. When n = 1, this variety coincides with the class ofω-semigroups of Perrin and Pin.Moreover, we show that those Σ-labeledn-posets that can be generated fromthe singletons by the binary product operations andthe ω-power operations form the free algebra on Σin a related variety that generalizes Wilke's algebras.We also give graph-theoretic characterizationsof those n-posets contained in the above free algebras. Our resultsserve as a preliminary study to a development of a theory ofhigher dimensional automata and languages on infinitaryassociative structures.