Dynamic Modeling Method of Flexible Workflow Based on Expanded ECA Rule

and Its Application

LI Zhi-qiao, WANGShu-hai, HAN Li-hua, QI Zhao-hui College of Information Science and Technology

ShiJiaZhuang TieDao University ShiJiazhuang

wangsh@sjzri.edu.cn

Abstract-Traditional workflow system is not able to meet the

need of dynamicity and adaptability. This paper proposes a

dynamic modeling mechanism of flexible workflow based on expanded Event-Condition-Action (EAC) rule. The mechanism can be used to dynamically construct workflow

model including cycle logic and build up one adapted to the requirement for E-government system flow. Finally, we give a

practical example about Hebei science & technology awards evaluation system to demonstrate the validity of this method.

Keywords-flexible workflow; dynamic modeling; EAC rule; science & technology awards evaluation system

I. INTRODUCTION

The traditional workflow models only express the process down the linear route. In fact, one can need to implement dynamically route generally. So it requires that the workflow model can express different processing methods. In the business process of E-government system, the events always follow each activity to execute. The workflow model needs to choose opportune action to execute according to the event-condition-action rule, when a event had happened. The complexity and uncertainty of administrative management requirement make it difficult for the traditional administrative management system to meet the interoperability and flexibility of administrative management.

This paper constructs a dynamic model of flexible workflow based on expanded ECA rule. The ECA rule is a rule that some events execute their actions under certain conditions. The expanded ECA rule adds two elements that role and business based on the ECA rule. That is, the expanded ECA rule is one that some events execute their actions under certain conditions when some roles are executing in some objects[l]. The expanded model inherits the characteristics of ECA in the dynamic interaction.

The expanded ECA rule not only improves its ability to describe objects in complex business process, but also further meets the requirements for complex process modeling of many users in management system. In the modeling process, the workflow instances can be dynamically generated. To a certain extent, the model resolves the problem that the workflow can not be fully defined before running. Then it achieves the dynamic deployment of workflow by modifying the model definition.

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II. FLEXIBLE WORKFLOW

A. Flexible worliflow definition

The flexible workflow is a workflow that it can dynamically adapt to changes in administrative management processes without re-defining by the workflow model definition and the workflow machine running. The flexible workflow dynamically alters the executing path according to workflow activities and relevant data without interrupting the process of administrative management. And it has the adaptability [3].

B. Flexible worliflow model

There are two types of actIVItIes in the flexible workflow model. One is the ordinary activity which is clearly defined in the modeling phase. The other is the flexible activity which is not likely to be beforehand given a complete definition. A flexible activity represents an activity or a sub-process [4].

Atlexible worldlow is a four-tuple FP = (ID, D, A, E) . The meaning of each element is as follows.

ID : It is a unique identifier of process definition which is used to distinguish dynamic process definitions;

D : It is a general description of flexible process which includes the creator of the process definition, the created date of the process definition, the version of the process definition and so on;

A : It is a set of process activity which includes ordinary activity and flexible activity;

E : It is a set of ECA rule, where E = (epe 2 , e 3 , ••• , eJ. It defines some transfer conditions among different activities.

Each activity is described by a three-tuple < NAME, TYPE, SACS >. NAME is the name of activity. TYPE is the type of activity which includes the ordinary activity or flexible activity. SACS is null when the activity is ordinary activity. SACS includes the rules that must be followed in the specific process of flexible activity when the activity is flexible activity.

SACS i is described by a two-tuple < AI;, SCR i >.

1) The AI; is a set which is composed of the select activities in the process of flexible activity instance. It is called as an activity pool, where its value is ( a a ... a ) l' 2' , n •

The activity can dynamically change in the process of activity instance.

2) Tre SCR j is a set of constraint rules, where SCR j =

(sclj, scr 2 , " ' , scr n ) ' It is a constraint set which consists of

some select activities. The select activities exist in the AI; . The four types of the constraint rules are shown in Figure 1 [3,41.

Then we specify four types of the constraint rules as the following.

a) a - b : If activity a and activity b are selected,

activity a executes when activity b has executed. The

structure is shown in figure 1 (a).

b) a -+ b: If activity a and b are selected, activity b

must be executed after activity a has executed. The structure is shown in figure 1 (b).

c) a=> b: If activity a and b are selected, activity b

must be immediately executed after activity a has completed. The structure is shown in figure 1 ( c).

d) c�: The activity c is the export of cycle logic node.

The structure is shown in figurel (d). a -+ b -+ c� -+ . . . n -+ a

is a cycle sequence. Node a is the loop entrance of the rule and node c is the loop export of the rule.

� ... � � ... -+GJ� a is in front of b

(a) a-b b is in front of a

-+GJ--. ... � a and b are adjacent

(b) a->b a and b are not adjacent

� � ... :[b a and b are adjacent a loop sequence

(c) a=>b (d) c6 Figure I. Four type of the constraint rules.

3) The extended ECA rule was formally defined, where ECA = (E, R, B, C, A) . The E shows the event which will happen. The R indicates the current role. The B shows the business object when the events are occurring. The C shows some conditions. The A shows a set of actions which is to be executed after some activities meet the rule.

The expand ECA rule is a rule that some events execute their actions under certain conditions when some roles are executing in some objects [51.

C. Description o/the WFMC model based on the extended ECA rule

The workflow definition based on the extended ECA rules has the good description ability. It can describe six basic types proposed by Workflow Management Association. They are six structures: sequence structure, or branch structure, or mergence structure, and branch structure, and mergence structure and loop structure. It can

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describe the complex relations by the appropriate combination [51.

Here are some brief descriptions. 1) Sequence structure

The structure can describe the execution of the activity b when the role R is executing in object B . The activity b starts if activity a has stopped. The ECA = ( a has stopped, R , B , true, b starts).

2) Branch structure The structure can describe the execution of the activity

b under the condition I when the role R is executing in object B . The activity b starts if activity a has stopped. The ECA = (a has stopped, R , B , Condition\, b starts).

The structure can describe the execution of the activity c under the condition2 when the role R is executing in

object B . The activity c starts if activity a has stopped. The ECA = (a has stopped, R , B , Condition2, c starts). 3) Mergence structure

The structure can describe the execution of the activity c when anyone of the activity a and the activity b has finished.

ECA = (a has stopped, R , B , true, c starts) or ECA =( a has stopped, R , B , true, c starts).

The branch is the relation between a node and its follow-up node. The aggregation is the relation between a node and its precursor node. The node is a node such as a or a branch node. The node is a node such as b or a mergence node.

III. FLEXIBLE WORKFLOW MODEL WITH CYCLE LOGIC

The steps of workflow modeling are the following. 1) Whether the rule needs to construct loop logic or not.

If it is not necessary, the selected activities construct diagram according to AUTOMATION_COMPOSITION, which is included in the literature 4. If it is necessary, the selected activities firstly construct the loop logic structure. Take the rule a -+ b� -+ c -+ .. . n -+ a as an example. The logical process is the following [31.

CDOne needs to add a new node or an aggregation node in front of node a, and add a new node or a branch node behind node b in the rule a -+ b� -+ c -+ ... n -+ a .

®One needs to replace the directed side from the node n to node a with one that the node n points to or aggregation node, replace the directed side that the node b points to node c with one that the node b points to or branch node, then separately add two directed sides that or branch node points to node c and or aggregation node points to node a.

®One needs to add other rule sides. The loop logic process is shown in Figure 2.

Figure 2. Loop logic diagram.

2) One needs to replace the directed sides that some nodes point to node a with one that some nodes point to or aggregation node in other rules, and replace the directed sides from node b to other nodes with one that or branch node points to other nodes in other rules.

3) One needs to connect the nodes according to other rules. The rules are the following:

CDIf the rule is a -b , connect the two nodes with a non­binding straight line.

®If the rule is a � b or a => b, connect the two nodes from node a to node b with a directed line.

Here only analyze a � b rule. The connected methods are the following:

CDIf the rule is a � b and node a, b are not in any loop, connect the two nodes from node a to node b with a directed line.

®If the rule is a � b and node a is in a loop, there are two branches after node a has executed. They are selected execution and parallel execution, respectively. If someone chooses a selected execution, he can add a node or a branch node, and connect the directed side which node a points to or branch node, and add a directed side that or branch node points to node b at the same time. If the choice is a parallel execution, he can add a directed side that node a points to nodeb.

®If the rule is a � b and node b is in a loop, the case is a case that node a is in the loop.

@If the rule is a � b and node a, b are in a loop, then it executes according to the construction (1) of step CD, ®, ®.

4) One needs to analyze all the loops. If there is the parallel output in the loop and its point is not in the loop, someone should traverse the tree, the node of which is not in the loop and is the root node. In the process of traversing the whole tree, one needs to add a directed side to which a leaf node points to the node which one specified when traversing each leaf node.

5) One needs to analyze all the nodes in the figure and do some operations:

CDIf out-degree of the node is 0 or the node is or branch node and in-degree is 1, one should connect a directed side from the node to the end.

®If in-degree of the node is 0 or the node is or aggregation node and in-degree is 1, one should connect a directed side from the start to the node.

®If in-degree of the node and out-degree of the node are 0, one should connect a directed side from the start to the node, then connect a directed side from the node to the end.

IV. MODELING EXAMPLE

The paper takes the modeling of peer evaluation phase in Hebei science & technology awards evaluation system as an example. The process of specific evaluation is shown in Figure 3.

One only knows general framework of the process and some of activities involved in the process, such as viewing

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project materials, seeing the evaluation document, etc .. Because the evaluation rounds and methods are influenced by award policy and business requires, one can not beforehand give complete definition. But one can dynamically add events and rules. So one needs to create and select activities and rules in the evaluation process, then one specifies the sub-process step by step.

In the phase of peer evaluation, the user roles are evaluation experts, managers, etc .. So this paper instantiates the workflow model based on the extended ECA rule according to AUTOMATION_COMPOSITION algorithm [4] and loop logic rules. The paper only implements the modeling process with the role of evaluated experts. The specific instructions of the process are the following:

1) AdivityPoolA = (a\ , a2 , a 3 , a 4 , a 5 , a 6 , a 7 , as , a 9 , alO � There are accreditation entrance, expert login, viewing the simulated project material, simulating-rate, submitting the rate-results, analyzing the rate-result compared with previous years, viewing project materials, submitting the project rate-results, viewing the rate-results, viewing accreditation document and updating personal information of experts, respectively.

Figure 3. Peer evaluation diagram.

2) Constraint rules of the activity pool SCR = {scr \ , scr 2 , scr 3 , scr 4 , scr s};

scr\=a \�a2;

scr2=a 2�a 6�a 7�aS!1�a2;

scr 3 = a 2 � a 3 � a 4 � as;

scr 4 = a 2 � a 9 ; scr 5 = a 2 � a 10 ;

3) Specific descriptions of the extended ECA rule E = (e \ , e 2' e 3' e 4' e 5' e 6' e 7' e s , e 9' e 10 ) ;

e \ = ( a \ has stopped, R, B, true, a 2 starts) ;

e 2 = (a 2 has stopped, R, B, ConditiionI, a 6 starts) ;

e 3 = ( a 2 has stopped, R, B, Conditiion2, a 3 starts) ;

e 4 = ( a 3 has stopped, R, B, true, a 4 starts) ;

e 5 = ( a 4 has stopped, R, B, true, a 5 starts) ;

e 6 = ( a 2 has stopped, R, B, Conditiion3, a 9 starts) ;

e 7 = ( a 2 has stopped, R, B, ConditiioI4, a \0 starts) ;

e 8 = ( a 6 has stopped, R, B, true, a 7 starts) ;

e 9 = ( a 7 has stopped, R, B, true, a 8 starts) ;

e \0 = ( a 8 has stopped, R, B, true, a 2 starts); 4) Construct the flexible workflow model

(DOne needs to construct the workflow model with the loop logic and connect the rest of nodes according to the rest rules. The loop logic diagram is shown in Figure 4.

®when he analyzes the scr 3 , scr 4 , scr 5 rules, one can

determine that the node a 2 is in the loop logic. But one can

not determine that whether the relation between a 2 and a 3 , a 2

and a 6 , a 2 and a 9 ' a 2 and a \0 is a selected execution branch or a parallel execution branch.

Figure 4. Steps I has perfonned.

a) If the choice is the selected execution, one needs to add a or branch node behind the node a 2 according to step

3 and then replace a directed side that node a 2 points to

a 6 , a 3 ' a 9' a \0 with one that a 2 points to or branch node, then respectively add the directed side that or branch node points to a 6 , a 3 ' a 9' a \0 • The diagram is shown in Figure 5.

'----+I .001---------'

Figure S. StepS has perfonned (step3 is selected execution).

b) If the choice is the parallel execution, one needs to respectively add the directed sides that node a 2 points to

a 3 , a 9 , a \0 according to step3. Every branch executes in

parallel behind node a 1 .One needs to traverse the tree that

a 2 is the root node and add three directed sides that node

a 3 , a 9 and a \0 respectively points to node a 8' Then one appends the rest of sides. The diagram is shown in Figure 6.

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Figure 6. StepS perfonned (step3 is parallel execution).

It needs to add a temporary activity at which the leader and secondary leader offer the comprehensive suggestion between a 7 and a 8 according to users requires. Then we only modify and add some rules. All the activities are defined beforehand.

The constraint rules are modified in the flexible activity pool. That is the rule scr2=a 2�a 6�a 7�a8Ll�a2 is modified that rule

scr2 = a2 � a6 �a7� at � a8� � a2 ; In the description of the expanded ECA rule, one

needs to change the rule that e 9 = (a 7 has stopped, R, B,

true, a 8 starts) to the rule that e 9 = (a 7 has stopped, R, B, true, at starts).!t needs to add a description of the rule at the

same time. That is ell = (at has stopped, R, B, true, a 8

starts). It realizes the modeling examples according to the

expanded ECA rule. The model is independent of the business process and can affect some business processes; one can deploy dynamically according to the expanded ECA rule, which makes the process logic change dynamically. The process logic is independent on Implementation of the logic. It needs to modify simply the existing rule to implement the change when the work process can not meet current demand.

V. SUMMARY

This article constructs a flexible workflow model by the extended ECA rule based on automatic combination of algorithm and the loop logic modeling idea. And the model is used in Hebei science & technology award system. The model makes its adaptability more extensive and increases the activity concurrency to a certain extent. At the same time, it significantly improves the award system on interoperability, agility and flexibility.

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