Manufacturing companies spends an increasing amount of the total work resources in the manufacturing planning system with the activities of e.g. specifying products and methods, scheduling, procurement etc. By this the potential for obtaining increased productivity moves from the direct costs in the production to the indirect costs in the manufacturing planning system. This Ph.D.-project consider information technology (IT) to be an important means for obtaining increased productivity and efficiency in these functions. The project focuses on the use of IT to support the activities of specifying products and methods, as only a minor part of the engineering work in these functions in the planning system until now has been supported with IT. The aim is to develop methods for analysing which activities to support with IT, and in relation to this, define context and structure of the IT-systems to support the specification work. The theoretical fundament of the project include four elements. The first element (work preparation) consider methods for analysing and preparing the direct work in the production, pointing to an analogy between analysing the direct work in the production and the work in the planning systems. The other element covers general techniques for analysing and modeling knowledge and information, with special focus on object oriented modeling. The third element covers four different examples of product models. The product models are viewed as reference models for modeling knowledge and information used for specifying products and methods. The last element attach to the use of the task concept viewed as a means for expressing the demands to a given system in the company. In this case, systems for specifying products and methods. Based on the referred theory, the project provides a line of procedure for developing systems to support the specification activities in the company using product models. The first phase in the procedure contain an analysis of the task of the system (called the product and methods specification task) leading to a definition of the context and structure of the system in the specific company. The following phases are based on the use of object oriented mode-ling and follow in outline the object oriented project life cycle. The empirical work in the project, carried out at Alfa Laval Separation A/S, covers all the phases in the line of procedure from analysing the task of the system, over building a model, and to the final programming of an application. It has been stressed out to carry out all the phases in the outline of procedure in the empirical work, one of the reasons being to prove that it is possible, with a reasonable consumption of resources, to build an application to support a part of the specification work in the company.