Concurrent versioning of source code is a common and well-established practice to manage concurrency and consistency within source code repository. With the growing complexity of nowadays software systems, the need for high level representations of the system to develop becomes inevitable. These software models evolve together with the software system, thus requiring versioning management. Moreover, software models are often the result of cooperative work by different software engineers, that need to update them even concurrently.Unfortunately, the available concurrent versioning tools, do not provide an adequate support for this type of software artifacts. We propose a solution to manage versioning and concurrency for software models (in particular, UML models), that consists of a fine-grained concurrent modeling approach. The approach has been implemented and integrated in an artifact management system, thus also enabling reuse of model elements across the entire project.