There is a great interest paid to the web services paradigm nowadays. One of the most important problems related to the web service paradigm is the automatic composition of web services. Several frameworks have been proposed to achieve this novel goal. The most recent and richest framework (model) is the Colombo model. However, even for experienced developers, working with Colombo formalisms is low-level, very complex and timeconsuming. We propose to use UML (Unified Modeling Language) to model services and service composition in Colombo. By using UML, the web service developer will deal with the high level graphical models of UML avoiding the difficulties of working with the low-level and complex details of Colombo. To be able to use Colombo automatic composition algorithm, we propose to represent Colombo by a set of related XML document types that can be a base for a Colombo language. Moreover, we propose the transformation rules between UML and Colombo proposed XML documents. Next Colombo automatic composition algorithm can be applied to build a composite service that satisfies a given user request. A prototypical implementation of the proposed approach is developed using Visual Paradigm for UML.