In the literature on configuration there is a consensus about the nature of configuration tasks. Most definitions of a configuration task found in the literature are a slight variant of [Mittal & Frayman, 1989]:
``Given: (A) a fixed, pre-defined set of components, where a component is described by a set of properties, ports for connecting it to other components, constraints at each port that describe the components that can be connected at that port, and other structural constraints; (B) some description of the desired configuration; and (C) possibly some criteria for making optimal selections.
Build: One or more configurations that satisfy all the requirements, where a configuration is a set of components and a description of the connection between the components in the set, or detect inconsistencies in the requirements.''
The configuration task can be considered as a search problem using the above types of inputs and output [Löckenhoff & Messer, 1994] The configuration process restricts this search space in four steps using the various types of inputs (see Figure 2). The set of possible components and the possible connections between these components are fixed and given beforehand. This restricts the search space to the possible configuration space. The constraints restrict this possible configuration space to the valid configuration space. The user-requirements restrict this valid configuration space to the suitable configuration space. The optimality criteria can possibly restrict or divide this space further.
Figure 2: Configuration task as search problem
Parametric design is a simplification of the configuration task (class 3 problem). In parametric design are only fixed structures and fixed components. A components is a parameter which have a particular range that is given before hand. This reduces the configuration problem, because we only have to assign values to a parameter in its own range. (See [Wielinga et al., 1995] for a detailed analysis of parametric design).