The NSF Center for e-Design, Brigham Young University (BYU) site has re-architected Computer Aided Design (CAD) tools, enabling multiple users to concurrently create, modify and view the same CAD part or assembly. This technology allows engineers, designers and manufacturing personnel to simultaneously contribute to the design of a part or assembly in real time,enabling parallel work environments within the CAD system. Multi-user systems are only as robust and efficient as their methods for managing conflicts and preserving model consistency. Conflicts occur in multi-user CAD when multiple users interoperate with the same or dependent geometry. Some conflicts can lead to model inconsistencies which means that each user's instance of the model are not identical. Other conflicts cause redundant work or waste in the design process. This dissertation presents methods to avoid and resolve conflicts which lead to model inconsistency and waste in the design process. The automated feature reservation method is presented which prevents multiple users from simultaneously editing the same feature, thus avoiding conflicts. In addition, a method is also presented which ensures that copies of the model stay consistent between distributed CAD clients by enforcing modeling operations to occur in the same order on all the clients. In cases of conflict, the conflicting operations are preserved locally for manual resolution by the user. An efficient model consistency method is presented which provides consistent references to the topological entities in a CAD model, ensuring operations are applied consistently on all models. An integrated task management system is also presented which avoids conflicts related to varying user design intent. Implementations and results of each method are presented. Results show that the methods effectively manage conflicts and ensure model consistency, thus providing a solution for a robust multi-user CAD system.



College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering



Date Submitted


Document Type





Multi-user CAD, synchronous collaboration, data consistency, conflict management