Both quantitative and qualitative models can be either deductively or inductively constructed. Deductive modeling requires a priori knowledge of the mechanisms that are responsible for the dynamic system behavior. Using this knowledge, a model can be derived from which system behavior can be deduced. From this data, possible mechanisms that would explain the observed behavior may be deduced. Purely inductive quantitative models are hardly ever used.
Any quantitative model requires some prior assumption about the model structure.
If no other information is available, usually a linear structure is assumed. However, if a linear structure does not explain the observed behavior well, and if nevertheless no structural knowledge is available that can be used for the construction of a quantitative model, a qualitative inductive model may be the right choice. Since inductive models require less information for their construction, qualitative inductive models can be constructed without presupposing structural information.