Concurrency control has always been one of the most important issues in the design of synchronous groupware systems with fully-replicated architecture. An ideal strate- gy should be able to support natural and flexibl...Concurrency control has always been one of the most important issues in the design of synchronous groupware systems with fully-replicated architecture. An ideal strate- gy should be able to support natural and flexible human-to-computer and human-to-human interactions while maintaining the consistency of the system. This paper summarizes previ- ous researches on this topic and points out the deficiencies of the existing results. A novel semantics-based concurrency control framework, oodOPT is proposed. The main idea of the framework is to resolve conflicts by utilizing semantics of the operations and the accessed data objects. With this approach, complexities in concurrency control are shifted completely from application developers to the framework. Conflicts among operations on objects with different semantics and the strategies resolving these conflicts are analyzed. After describing the algo- rithm in full detail, the discussion ends up with a comparison with other related work and some considerations for open problems.展开更多
In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by th...In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by the method is carried byintensively using model's structural information, such as invariants, siphons, etc.. As aresult, the analysis leads us to draw the general conclusion that the model obtained isconservativeness and thus bound, and characterize its liveness in terms of zero-markingminimal siphons. It is based on model's structural information that distinguishes ourmethod from others. in line of this thought, a liveness guarantying policy for the obtainedmodel is proposed. Some control subnets are merged into the original model according tothe proposed synthesis rules in this paper to ensure that no minimal siphons are emptiedin any state, therefore the liveness is guaranteed. As a result, a live, conservative andrevertible Petri Nets is obtained. A practical example is also presented to demonstrate theeffectiveness of this method.展开更多
基金The work was supported by the National Natural Science Foundation of China under grant No.69773029 and theNational '863' High-
文摘Concurrency control has always been one of the most important issues in the design of synchronous groupware systems with fully-replicated architecture. An ideal strate- gy should be able to support natural and flexible human-to-computer and human-to-human interactions while maintaining the consistency of the system. This paper summarizes previ- ous researches on this topic and points out the deficiencies of the existing results. A novel semantics-based concurrency control framework, oodOPT is proposed. The main idea of the framework is to resolve conflicts by utilizing semantics of the operations and the accessed data objects. With this approach, complexities in concurrency control are shifted completely from application developers to the framework. Conflicts among operations on objects with different semantics and the strategies resolving these conflicts are analyzed. After describing the algo- rithm in full detail, the discussion ends up with a comparison with other related work and some considerations for open problems.
文摘In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by the method is carried byintensively using model's structural information, such as invariants, siphons, etc.. As aresult, the analysis leads us to draw the general conclusion that the model obtained isconservativeness and thus bound, and characterize its liveness in terms of zero-markingminimal siphons. It is based on model's structural information that distinguishes ourmethod from others. in line of this thought, a liveness guarantying policy for the obtainedmodel is proposed. Some control subnets are merged into the original model according tothe proposed synthesis rules in this paper to ensure that no minimal siphons are emptiedin any state, therefore the liveness is guaranteed. As a result, a live, conservative andrevertible Petri Nets is obtained. A practical example is also presented to demonstrate theeffectiveness of this method.
