Kairos Planet - Terms of Payments

Proceedings of the 10th International Conference on Computer Supported Cooperative Work in Design The Specification of Workflow Activity Multiple Instances** Ruizhi Sun', Guangli Liu', Meilin Shi2 'College ofInformation and Electrical Engineering, China Agricultural University, Beijing, China sunrz@cau. edu. cn, liugl@cau. edu. cn 2Dept. of Computer Science and Technology, Tsinghua University, Beijing, China shi@csnet4. cs. tsinghua. edu. cn Abstract Performing multiple instances of one activity will enable workflow management system to be flexible on handling workflow process. When handling multiple instances the main problem is the synchronization of workflow activity instances. After analyzing the assignment and the join of multiple instances, this paper describes the patterns of multiple instances, and classifies the basic patterns into four types. Then from the point of view control of instances joining, instance splitting and triggering the next activity instance, we pick four elements up that affect the process 's progress. The four elements can be used as the uniform denotation to show the characteristics of multiple instances. The formal presentation of activity attributes of multiple instances will enable a workflow engine to handle the activity instances simple and unifiable. Keywords: Multiple Instances, Workflow, Workflow Management System, CSCW 1. Introduction In Workflow Management System (WfMS), a pre-defined process can be instantiated more than one time. One execution of a process is called a process instance. Accordingly, one activity instance means the work item associated to an activity is dispensed to a user and multiple instances mean the multiple work items derived from one activity dispensed. The instances derived from one same activity can be classified into two types, one is that these instances come from one activity in the same process instance, the other is that these instances can come from one activity but in the different process instances and these process instances share the same workflow scheme. The later is insignificant to discuss because these activity instances are controlled by different process instance and they are performed independently, whereas the former is meaningful for their coordination behavior. The multi-instances of an activity mean that one activity in a process instance is performed many times by different users and perhaps only all the activity instances are submitted by their performers that the activity task be finished. For example, in a voting program, only when all numbers of voter poll that the vote activity can be thought as valid. When we design a workflow engine that can handle multi-instances, one problem confronted is how to control the synchronization of those activity instances. To do it, the correct semantic of instances is critical. So, in this paper we focus on the specification of activities with multiple instances to provide the guide to control and schedule a workflow process. The paper is organized as follows. The next section discusses related work in multiple instances of workflow. In section 3, we describe the various patterns of multiple instances of workflow activities, and based on these patterns, section 4 gives the specification of multiple instances patterns from the point of view controlling and scheduling instances and finally is conclusions. 2. Related work Although the concept of multiple instances is not creative, to our best knowledge, the literature addressing activity multi-instances of workflow is few. W.M.P. van der Aalst et.al summarized the workflow patterns. They classified the patterns into 8 classes including 26 sub-classes E'l. According to the time of figuring out the number of instances, they classed the multi-instance into 3 patterns, they are (1) on the time of defining scheme, (2) on the time of performing of process and (3) until the time of instantiating workflow activity. But the article only give the catalogues of instances, not giving the propose how to schedule the instances. A.P.Barros and A.H.M. ter Hofstede studied the issues of trigging the instances of a process and sorted the model of trigging instances into the synchronous messaging and asynchronous messaging from the point view of message transferring [. In their literature, a method of abort is proposed to end the instances of a process, and a process is set exclusive to avoid the confliction of accessing the shared data by instances. Also W.M.P. van der Aalst et. al studied the relationship of multiple entities and proposed the concept of Proclet based on the entity-relationship 3]. A Proclet is a segment of process. The instances of Proclet can be triggered multiply by performative. 1-4244-0165-8/06/$20.00 C 2006 IEEE.

Kairos Planet - Terms of Payments

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