Concurrent/reactive systems can be designed free of deadlock using prioritized
service architecture (PSA), subject to simple, statically verified, design rules.
The Honeysuckle Design Language (HDL) enables such service-oriented design to be
expressed purely in terms of communication, while affording a process-oriented implementation,
using the Honeysuckle Programming Language (HPL). A number of enhancements
to the service model for system abstraction are described, along with their
utility. Finally, a new graphical counterpart to HDL (HVDL) is introduced that incorporates
all these enhancements, and which facilitates interactive stepwise refinement.