A configuration problem within the technical domain is the problem of putting together different parts into a complex system, given a description of the possi-ble parts and the functionality of the required sys-tem. While workin~ with our master thesis (Leitgeb, Pernler 95) at SICS ~ during 93 and 94, we found only a few configuration systems extracting the functional reasoning from the structural. We herein motivate the need for functional reasoning as a basis to find meaningful control structures sep-arated from the application domain knowledge, and that this, together with a separated structural ap-proach to describe the possible parts of the artefact, might be a neat solution. We have defined a model for representing configura-tion problems in two dimensions: Functional knowledge of the function of the artefact. Structural knowledge about structure and possible parts of the artefact. We have named this model the FAST model--the Functional And STructural model, and tested it on a real world application.