Research On Key Techniques Of Synchronized Collaboration Among Heterogeneous CAD Systems

Integrated with the Computer Aided Design (CAD) technology and Computer Supported Cooperative Work (CSCW) technology, the collaborative CAD, which is able to shorten the product development time, makes best use of remote resources and reduces the design cost, has made a rapid and further progress in the past decade. The synchronized collaborative design among heterogeneous CAD systems becomes a significant challenge because of the great difference between the modeling operations and underground data structures of different systems. In order to enable it, this thesis mainly researches on the approach to constructing synchronized collaborative design platform among heterogeneous CAD systems and the multi-versioning technique based on version replication for consistency maintenance.Considering the heterogeneity of CAD systems in distributed environments, a heterogeneous CAD collaborative model based on macro-semantics and the architecture for semantic interoperation among distributed CAD systems are presented. A Macro Semantic Commands based approach to building up a synchronized collaborative design platform upon heterogeneous CAD systems is proposed according to the extensive requiements of this technology. By analyzing the modeling commands and macro files of several commercial CAD systems, the definitions of Macro Command Group (MCG) and Macro Semantic Command (MSC) are given and a set of MSCs are developed. In this approach, the MCGs corresponding to the modeling operations of each CAD systems are exchanged by MSC in the form of XML. Moreover, two kinds of translators are established, which can deal with the translation between MCG and MSC.The multi-versioning technique based on object replication strategy can meet consistency model while the conflict operations occurring in the cooperative graphics editing systems (CGES), but it does not efficiently solve conflict between non-geometry attribute operations and complex graphics objects. A new distributed multi-versioning model based on version replication is proposed for consistency maintenance of discordant conflicting operations according to the conflicting features and types of concurrent operations in CGES. To guarantee intention of conflicting operations, leaf-versions must be replicated from the original version based on the reduce strategy, and then applying conflicting operations to the corresponding object of the different replicated versions. The leaf-versions can be created by Multiple Object Versions Incremental Creation (MOVIC) algorithm in which the comparison-number of compatible operations is too much. A Fast Multiple Versions Incremental Creation (FMVIC) algorithm based on the compatible and conflict group is presented in this thesis. The final versions constructed by the FMVIC algorithm is the same as that constructed by the MOVIC algorithm, but it can decrease the comparison-number of compatible operations and narrow the scope of comparison operations for the removing redundant versions.Finally, a prototype of synchronized collaborative design is developed based on two common CAD systems. The preliminary test results show the proposed approach works well for integrating various current popular commercial CAD systems into a synchronized collaborative design platform.