A Concurrency Integrity Model for Distributed Product Data Management.

摘要

A product data management (PDM) system is implemented to control the distribution and maintain the integrity of the product data throughout its entire life cycle. Multiple accesses to the system residing on multiple sites will cause concurrency problems. It is crucial that concurrency control must be provided to protect the data against a variety of possible threats, in particular, data inconsistencies must be avoided and relationships between data must be maintained. In particular, the current PDM technology is not completely suitable for PDM in distributed manufacturing environment. Thus, this research aims to develop a foundation in concurrent engineering support for distributed product data management (DPDM).;Given that the traditional concurrency control methods were not purposely developed to meet the need of DPDM, the requirements for data storage and manipulation for DPDM systems are not well supported. Therefore, a concurrent control method that caters for version management and product architecture in DPDM is proposed. This research demonstrates how granularity and versioning are incorporated into a lock-based concurrency control model. The concurrent accessibility of an example product data is explained to illustrate the adjustability according to the actions taken by the users and the architecture of the corresponding data object.;To validate the performance of the proposed methods, the strict two-phase locking (2PL) method, the two-phase granularity version (GV) locking method, the 2PL transaction scheduling method, and the hybrid GV transaction scheduling method are evaluated through simulation experiments. Read and Write accesses to composite objects are used to illustrate the comparisons between the models. Their performances are evaluated by comparing the number of late transactions. It shows that the GV locking model and the transaction scheduling model are better than the strict PL method while the hybrid model can substantially improve the concurrency of DPDM system.