In the integer programming model, structural identification and relaxation is an approach that generates the Lagrangian problem of the model. The approach is based on a semantic view which specifies the optimization model in a formal knowledge representation such as frames. We have developed a system, UNIK-RELAX, that implements the approach on the knowledge-assisted optimization modeler; UNIK-OPT, and forward chaining rule based system, UNIK-FWD. This paper particularly elaborates three states: The model distinctiveness state, embedded structure state and Lagrangian structure state which occurred in the process of generating the Lagrangian problem. The system UNIK-RELAX is applied to a data allocation model. (C) 1997 Elsevier Science Ltd.