In this paper we describe how existing software developing processes, such as Rational Unified Process, can be adapted in order to allow disciplined and more efficient development of user interfaces. The main objective of this paper is to demonstrate that standard modeling environments, based on the UML, can be adapted and efficiently used for user interfaces development. We have integrated the HCI knowledge into developing processes by semantically enriching the models created in each of the process activities of the process. By using UML, we can make easier use of HCI knowledge for ordinary software engineers who, usually, are not familiar with results of HCI researches, so these results can have broader and more practical effects. By providing a standard means for representing human computer interaction, we can seamlessly transfer UML models of multimodal interfaces between design and specialized analysis tools. Standardization provides a significant driving force for further progress because it codifies best practices enables and encourages reuse, and facilitates inter working between complementary tools. Proposed solutions can be valuable for software developers, who can improve quality of user interfaces and their communication with user interface designers, as well as for human computer interaction researchers, who can use standard methods to include their results into software developing processes.