Architecture Analysis And Improvement Of Open Source Workflow Engine Shark

With the development of the computer and network technologies,especially with popularization of Internet applications,workflow technology has obtained the widespread application.Enhydra Shark is a function formidable workflow engine, which entirely bases on the standards of Workflow Management Coalition and Object Management Organization and takes XPDL as process definition language.It has provided rich function components and interfaces and has good expansibility.This article,on the basis of refering to workflow reference model and workflow process definition interface XPDL,carried on introduction to the Shark architecture and the database structure in detail,then carried on the thorough analysis to the core interfaces and implements of Shark engine from the aspects of startup model,package management,process management,activity management,task authorization and core dispatch algorithm.The database persistence of Shark is implemented by DODS,which is also one of products in Enhydra series as Shark.However there are many defects in DODS, such as difficulties in study,insufficient optimization of performance,low reusability. In view of these questions,a new kind alternative plan,which profitted from the existing outstanding persistent technologies was provided,i.e.hibernate which was a very popularly O/R mapping framework was used to substitute DODS to implement the Shark database persistence layer.And the realization process was given in detail. The solution not only enhanced the Shark performance,but also is helpful to carry on integration and application with other systems widely.The Shark authorization control model is similar to the role based access control model(RBAC).In addition the limitation of XPDL criterion causes the authorization function which the engine has implemented to be quite weak.The concrete improvement program was provided in view of these questions,basically solved the defects,e.g Shark authorization had not to manifest the dynamic nature,lacked of the authorization strategy,and disabled the authorization granularity to achieve task access level.Simultaneously the re-authorization function was extended and has facilitated in the system application authorization management enormously.The research contents and solutions in the paper have obtained the preliminary application in the actual E-government OA system and have made good effect.