An instance of a flow definition language for designing an integrated
circuit implementation flow. The instance of the flow definition language
includes a hierarchical collection of stages for a physical chip design.
Relational constraints define the execution order of a plurality of tasks
in the hierarchical collection of stages. Parameters customize the
plurality of tasks. The relational constraints and parameters are
hierarchically defined, such that higher order definitions in the
hierarchical collection of stages override lower level definitions of the
relational constraints and parameterized knobs.