A TIME MANAGEMENT METHOD IN WORKFLOW MANAGEMENT SYSTEM

Pegah Hamidkhani MianjiStudent no: 92131562

In the name of God

BPR PresentationThought by: Dr. Alireza Hashemi

Intro• Competition In Market Environment• Change from Cost and Quality to Flexibility and

Responsiveness• Workflow management systems provides the foundation

for defining and executing business Processes• The time constraints and time management are very

important

Workflow model + Time Constraints

Overview

In this Presentation will see:• 6 time constraints in workflow modeling• Workflow routing and Control Condition• Calculate critical Path in build time

• Forward Calculation• Backward Calculation

• Calculate critical Path in run time• Forward Calculation• Backward Calculation

• A solution for uncertainty of execution time• Conclusion

Workflow Model• A collection of activities and dependencies among

activities• Some Model definition Tools: Petri Nets , XPDL• Here we use directed graph:

• N: Activity• C: Edge

• The activity is denoted by:• D: I/O Data• E: executor• R: resource• T: time constraint

• In this presentation we focus on time constraints

Timed constraints

• Time Duration: The time span from the activity is inactive state to completed => Compulsory

• Forced start time: Is the time that an activity should be executed after it

• Deadline: Is a time that an activity be completed• Fixed Date Constraint: An activity can only be executed

on certain fixed dates. For example: every Mondayleft bound of constraint

right bound of constraint

Timed constraints• Time Difference: the time difference between two

activities is caused by different time zones• Time Distance: the time duration between activity A1 and

A2, where A1 is the predecessor of A2

We show them like :

The Value of each time constraint, if exist, is assigned by the workflow designer according to the experience value in build time.

Control Routing

Iteration Time Duration• Probability of iteration: p• Total average execution time: T

A2

A4

A1 A3

Workflow Critical path• We use extended Critical Path Method (CPM) with time

constraints considered

: earliest start time of an activity

: earliest finish time of an activity

: latest start time of an activity

: latest finish time of an activity

Depending on control dependencies between activities in workflow these are calculated

Rules In Critical Path Computation• Assume A and B are two adjacent activities and A is the

predecessor of B• of B is of A plus the time duration of A• If some time distance required the of B is:

• If they are in different time zones, the time difference must be taken into account• If time zone B is in the working hours

• Or, time zone B is not in working hours

Rules In critical path computation• If there is a fixed date constraint on activity B, we have

two situations:• If the time is located in the space of the fix date

• else

Build Time Calculation Considerations

• Time constraints according to the experience or estimated value

• We treat all routing controls as AND-Split / AND-Join• The forced start time, deadline and time difference can’t

be identified because workflow is static

Build Time Calculation (Forward)

Build Time Calculation (Backward)

Runtime Calculation Considerations• Start time is real and the time information of all the other

Activities can be Identified• All six time constraints should be taken into account• All OR-Split/ OR-Join pair will be checked• So a new graph is given for calculation

• (for time difference constraint) and (for fixed date constraint) can be figured out exactly

Runtime Calculation (Forward)

Runtime Calculation (Forward)

Runtime Calculation (Backward)

Runtime Calculation (Backward)

Benefits Of Time Management• After Identifying the critical path of a workflow process we

can benefit from it• Workflow designers:

• Find bottlenecks and try to optimize the process• Find any potential time constraint conflict and resolve error

• Workflow managers:• Adjust the time plan according to time constraints• Schedule the activities in the work in the work list to enhance the

throughput• Monitor the execution and be alerted about potential time error• Adjust the execution of workflow instance if any time constraint is

violated

Time Constraint Violation

Deadline violation: the activity can’t be complete before it’s deadline

Four methods to overcome• Adjust the time durations of activities that are under

scheduling• Try to postpone the deadline of the very activity that will

be violated• Try to find another path to replace current path• If the former 3 methods can’t work the system will arouse

time exception and use exception handling

Forced start time error: system has to wait for certain time

Uncertainty of execution Time• We previously used experience or previous estimation but

this approach is very static• Estimate at process instantiation based on

• Executer• Instance

• Try to calculate the time extracted from history data or logs of existing WFMSs

• If no log exist get the time from who take charge of the related job

l=

Conclusion• We defined 6-tuple time constraints, to ensure that the

business process can be executed properly• The algorithm of identifying the critical path of certain

workflow process is given based on 6 time constraints• Benefits of time management described• How to face time constraint violation

Refrence• Weiping Li ; Sch. of Software & Microelectronic, Peking

Univ., Beijing ; Yushun Fan (2009) A Time Management Method in Workflow Management System, Grid and Pervasive Computing Conference.

Any Questions?