Research And Implementation Of Distributed Version Control Middleware

The distributed collaborative design technology is an effective method in large-scale engineer design with computer support. The design of large-scale projects such as aircraft collaborative design is an iterative process, so reliable and effective version control is especially important for distributed collaborative design. Version information not only records the evolution of the design process, but also provides technical support for the trace of design. Therefore, the research of distributed version control is of great theoretical significance and application values.This paper analyzes the key issues involved in distributed version control and focuses on the concurrency control and consistency strategy of transactions. The main achievements of this paper are listed as follows: 1. This paper proposes an adaptive decision concurrency control algorithm to solve the problem of poor adaptability in existing concurrency control algorithms. This algorithm divides its concurrency control process into two phases: the execution authorizing phase and the strategy selecting phase. In the execution authorizing phase, the algorithm compares effectiveness of transactions to determine the execution order of conflicting transactions. After that, the algorithm selects optimistic/pessimistic conflict resolution strategy dynamically according to the transactions' read/write status and the current conflict rate in the strategy selecting phase. ACC algorithm has high efficiency no matter whether the system is busy or idle. Performance tests show that ACC algorithm proposed in this paper is superior to classical strict two phases locking algorithm and hybrid concurrency control algorithm. 2. The traditional version control methods have the problem of poor universality, they can't be deployed distributed. To solve that, we proposed a semantic-based version control model. The pattern, version and relationship in that model dynamically describe the changing process of design objects. We also introduced the consistency constraints and the version management method. Experiments prove that the semantic-based version control model is superior to the other version control models in time and space overhead. 3. A distributed version control middleware on Eclipse platform is designed and initially implemented with the Jsp technology. There are experiments on and analyses of DVCM through aerocraft collaborative design software. The experiments show that models and algorithms designed in this paper are effective and feasible.