  We present a quasilinear time algorithm to decide the word problem on a
natural algebraic structures we call orthocomplemented bisemilattices, a
subtheory of boolean algebra. We use as a base a variation of Hopcroft, Ullman
and Aho algorithm for tree isomorphism which we combine with a term rewriting
system to decide equivalence of two terms. We prove that the rewriting system
is terminating and confluent and hence the existence of a normal form, and that
our algorithm is computing it. We also discuss applications and present an
effective implementation in Scala.
