  In reactive controller synthesis, a number of implementations (controllers)
are possible for a given specification because of the incomplete nature of
specification. To choose the most desirable one from the various options, we
need to specify additional properties which can guide the synthesis. In this
paper, We propose a technique for guided controller synthesis from regular
requirements which are specified using an interval temporal logic QDDC. We find
that QDDC is well suited for guided synthesis due to its superiority in dealing
with both qualitative and quantitative specifications. Our framework allows
specification consisting of both hard and soft requirements as QDDC formulas.
  We have also developed a method and a tool DCSynth, which computes a
controller that invariantly satisfies the hard requirement and it optimally
meets the soft requirement. The proposed technique is also useful in dealing
with conflicting i.e., unrealizable requirements, by making some of them as
soft requirements. Case studies are carried out to demonstrate the
effectiveness of the soft requirement guided synthesis in obtaining
high-quality controllers. The quality of the synthesized controllers is
compared using metrics measuring both the guaranteed and the expected case
behaviour of the controlled system. Tool DCSynth facilitates such comparison.
