  Blockchain technology has been proposed as a new infrastructure technology
for a wide variety of novel applications. Blockchains provide an immutable
record of transactions, making them useful when business actors do not trust
each other. Their distributed nature makes them suitable for
inter-organizational applications. However, proof-of-work based blockchains are
computationally inefficient and do not provide final consensus, although they
scale well to large networks. In contrast, blockchains built around Byzantine
Fault Tolerance (BFT) algorithms are more efficient and provide immediate and
final consensus, but do not scale well to large networks. We argue that this
makes them well-suited for workflow management applications that typically
include no more than a few dozen participants but require final consensus. In
this paper, we discuss architectural options and present a prototype
implementation of a BFT-blockchain-based workflow management system (WfMS).
