Advancement of engineering by computer systems in product development has reached full integration of model construction activities, models, and engineering processes. A recently recognized demand by product development against engineering systems is improved decision assistance. However, this requires computer intelligence that relies on local even personal knowledge and can not be built in a general purpose engineering system. Because of development of open system architectures and services in engineering or by conventional term CAD/CAM/CAE systems, capabilities for development of intelligence in application environments are available. The authors analyzed leading engineering informatics and proposed a set of methods for decision assistance. These methods are interrelated and integrable in professional engineering systems. Two main issues are definition of sets of parameters of modeled objects and management of frequent changes of modeled objects during product development. In the center of this methodology, constrained parameters act as restricting factors for modification of parameters of associative engineering objects. Paper starts with an outlook to engineering systems and preliminary results by the authors. Following this, groups of essential information in the proposed modeling are summarized and procedures for handling of that information are detailed. Next, construction of models in course of sequences of changes, and management of changes of modeled engineering objects, are explained. Changes are created or verified by behavior analysis. Finally, coordinated application of behavior analysis, intent combination, view creation, and change management is discussed to support decision-making processes.