1.)The design is mapped in four domains; Customer-,Function-,Design- and Process-domain. The Product or Process being designed is described in the Design domain hierarchically broken down in a design-tree. For each design parameter DP the functional requirement FR answering the question "why this DP?" is to be found in the same position in a function tree in the function-domain. For each DP also the process variable PV, that is chosen to create that DP, answering the question "how to get this DP?" is to be found in the same position in the process-tree in the process-domain.
2.)The functional requirements are related to the customer domain answering the question "how to satisfy the customer?" The functional requirements on the highest level have to be the minimum set of necessary functional requirements FR in order to meet the overall intention with the product in order to satisfy the customers. Each FR has to be specified quantitatively with tolerance.
3.)On each level in the product tree there is a one -to-one correspondence between FR, DP and PV. The tree-structure is the same in the function-, design- and process-domains. The question "how?" leads from FR to DP to PV and the question "why?" leads from PV to DP to FR.
4.)Depending on the choice of DP s, the FR s can be independent or dependent. The design can be uncoupled, decoupled or coupled in its functional behavior, depending on the choice of DP s. An uncoupled design is the easiest to operate. A decoupled design can be operated by setting the DP s in correct sequence. A coupled design finally requires iteration when setting the design-parameters and should be avoided. The degree of coupling can be seen in the design-matrix, which expresses the connection between the vector of DP s and the vector of FR s. Axiom 1: "Maintain independence between functional requirements." is referring to this fundamental connection between FR s and DP s. The same relation exists between DP s and PV s.
5.)A design specified in terns of DP s has a certain probability to meet specified FR s within given tolerances. A design with high probability to meet FR s within tolerances has also a high probability to satisfy customers and is therefore preferable. Axiom 2 "Minimize information content." is referring to this fundamental connection. Information content is here defined as log2(1/p) where p is the probability to meet the requirements. In an uncoupled design smallest sum of information content is equivalent with highest probability to meet all functional requirements within tolerances.
6.)Each level in the FR-tree is constrained by the next higher level in the DP-tree. In the same way each level in the DP-tree is constrained from the next higher level in the PV-tree. None of the trees therefore can be created independently. Zig-zagging over the three domains is necessary in the detailing of the design and the processes to create it.
This list of fundamental principles is set up by prof. Gunnar Sohlenius March 10 1998 after many years of contact with prof. Nam P. Suh who originally proposed the axiomatic principles of design.