+[slc:refSpecAttribute] > slc:executionSpecAttribute
+mixin
+// typically a class name
+- slc:type (STRING)
++ slc:value
++ * (mix:title)
+
+[slc:executionFlow] > nt:unstructured, mix:title
+- slc:name (STRING) ! m
+// if the execution spec is a referenceable node
+- slc:spec (REFERENCE)
+// if the execution spec is internal (without name)
++ * (slc:executionSpecAttribute) *
+
+// PROCESS