Optimization Based Computer Aided Modelling and Design : Proceedings of the First Working Conference of the IFIP TC 7.6 Working Group The Hague The Netherlands 1991 The working conference dealt with recent developments in the field of modelling and optimization and with knowledge based decision support systems. This contributed to the realiza tion of the aims of the working group 7.6 which are: to promote theoretical research in the field of optimization including mathematical programming and optimal control; to encourage the development of sophisticated knowledge based systems in which refined optimization models and algorithms are used; to contribute to the exchange and dissemination of information and collective experience among the inter ested groups and individuals; to support the practical ap plication of such systems in control engineering industry economy etc. A selection of papers is included into this proceedings vo lume since they reflect the current state of research in areas of interest to the field of (KB)DDS and or they are the value for the dissemination and exchange of information related to research topicsof interest and or they describe relevant practical experience related to designing buil ding implementing and using (KB)DSS