  Modeling is a key activity in conceptual design and system design. Through
collaborative modeling, end-users, stakeholders, experts, and entrepreneurs are
able to create a shared understanding of a system representation. While the
Unified Modeling Language (UML) is one of the major conceptual modeling
languages in object-oriented software engineering, more and more concerns arise
from the modeling quality of UML and its tool support. Among them, the
limitation of the two-dimensional presentation of its notations and lack of
natural collaborative modeling tools are reported to be significant. In this
paper, we explore the potential of using Virtual Reality (VR) technology for
collaborative UML software design by comparing it with classical collaborative
software design using conventional devices (Desktop PC, Laptop). For this
purpose, we have developed a VR modeling environment that offers a natural
collaborative modeling experience for UML Class Diagrams. Based on a user study
with 24 participants, we have compared collaborative VR modeling with
conventional modeling with regard to efficiency, effectiveness, and user
satisfaction. Results show that the use of VR has some disadvantages concerning
efficiency and effectiveness, but the user's fun, the feeling of being in the
same room with a remote collaborator, and the naturalness of collaboration were
increased.
