Design And Implementation Of Lightweight Workflow Management System Based On Metadata

With the rapid development of technology and the accelerated explosion of information, we must keep reforming and innovating to adapt the scientific research and the step of the society. Meanwhile, promoting enterprise to become the principle part of the technical innovation and transforming achievements to change the science and technology into the real productive forces are same important. The managed innovation has already become the premise of the technical innovation.In view of the fact that the platform of scientific management of the province-based government has not been established and put into practice, the program about the platform of the scientific project of management in JiLin province was authorized to set up in December 2004, after being testified by a group of experts organized by the Science & Technology Department of Jilin Province.Designing and realizing the platform system of scientific project of management in Jilin province is mainly purposed in this article. It accomplished a flow modeling of business process and established a complete set of normative model of flow through analyzing the flow of project management and the using of the Petri net modeling tool. Meanwhile, this article used J2EE constructing a light metadata-based workflow engine and realized the fundamental function of the workflow management system on the basis of MVC design patterns.The first step of the operation of the whole system is Workflow Modeling, which formalized the expression of Business Process, aiming attransforming the real Business Process into a standardized description of the flow. Through the using of one or more analysis, modeling and systematic technology, Business Process was changed into a definition that can be visited by a formalized computer. The results of that process are called Process Definition.Using the Petri net to model the workflow mainly relies on the Petri net's formidable modeling ability, which can be checked from the following aspects:1. Precisely semantic expressionThe Petri net-based model possesses precise meaning, because the Petri net is a mathematical model with accurate definition, which could be analyzed and testified from the point of semasiology and matrix theory.2. Graphical direct-viewing formPetri net is a kind of graphical language and has the characteristic of direct-viewing which is easy to learn. At the same time, Petri net is easy to be expressed by formalization, which is convenient for professionals to research and analysis.3. Formidable structure expression abilityAll the structures in the process of workflow modeling can be described by Petri net, which could express the state of the whole process.4. State-based description of casesThe Petri net is based on the conditions, which may clearly describe the state of the cases. We can judge whether the task was authorized, activated or implemented only by the distribution of token. This specialty ensures that the realization of the workflow engine is simplified.5. Abundant analytical methodsThrough the development of 30 years, the people had built many Petri nets based on analytical methods. These analytical methods may be used to confirm the security, the invariance, the soundness as well as the deadlock and so on. Also, they could be used to calculate each kind of parameter with different functions, like response time, standby period, occupation rates etc.. These analytical methods are also applied to the analysis of workflow.Workflow engine, which is the core of workflow management system, generates the flow instance for the user according to the process definition, drives the flow move according to the route defined and performs the access control to the users based on the logging identity according to the organization model and the definition of role's authority.The meta-data is introduced into the workflow engine and is used to specify the business data and the flow-specified document in this article. It processes the document flow by workflow engine and provides the control on business data. Furthermore, the business flow management and the business data management will be integrated organically.The workflow engine of the system is composed of five modules: the flow engine, the content management engine, graphical user interface, database interface and the database.The flow engine works in the runtime control centre, mainly plays the role of driving the flow move according to the route defined and modifying the corresponding business data. If some operation is performed on the business data in the flow definition, the operation will be sensed by the flow engine, which modifies the business data through calling the content management engine. The flow engine is composed of the parser and the executor.1. ParserThe function of the parser is to parse the Process Definition into data which can be executed and called by the executor. The Process Definition is stored in the tables of flow model in the form of records. The parser implements the call to the Process Definition through the database interface and parses it for it can be used by the executor.2. ExecutorThe executor is the key part of the whole work flow engine. It has a responsibility for actual execution of activity instances in the flow. It interacts with the outside resource to accomplish the concrete operation through the definition logic, in the activities, parsed by the parser. The execution of the flow and activities are guided by the rules of parsed-routes and the activities could be designated different transaction properties. When there is a need to operate the transaction data during the executor executes, the executor makes an interrupt and then calls the content management engine to do some responding operations for the transaction data which need to be dealt. After the content management engine finishes executing, the executor is called again. Afterwards, the executor will be going on executing according to interrupt parameters.Content management engine is in charge of accessing and retrieving the data definition in the meta-data table, operating the document data and the business data according to the flow definition, adding and modifying the business data. When adding records, content management engine will generate the flow instance according to the flow definition.The graphical user interface performs the access control to the user based on the logging identity, generates the corresponding work item andwork list, and displays the system errors and so on.The database interface builds the connectivity to the database and operates the corresponding item in the database, provides the interface program for the controller object, disables the access to the database directly.The database stores the process definition, flow data, and the business data. And the main function of the database interface is to establish the connection with database and to operate the corresponding item in the database.A novel conception of metadata is introduced to the workflow management system in this article. It is an effective solution to the traditional work flow management systems which are full of troubles in dealing with cooperation of process data and operational data.A set of lightweight work flow management system based on metadata is built in this article. Using the metadata to describe the process data and operational data, public documents, processes and business data processing will be integrated organically. The system would be strongly adaptable, expandable and widespread in many application areas.At present, the system still had many rules and logics concealing in the system frame and some fixed semanticses. The workflow engine still could not define discretionarily regarding the semanticses of process data manipulation. The future work of the article will focus on taking the noumenon as the foundation, realizing a uniform express for process flow model and the process data, implementing a stronger definition ability of data, flow rule and semanticses.