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.