Agent-based Workflow Management Systems (WfMSs) Company LOGO

Transcription

1 Agent-based Workflow Management Systems (WfMSs) Company LOGO JBees a distributed and adaptive WfMS with monitoring and controlling capabilities by Lars Ehrler, Martin Fleurke, Maryam Purvis, Bastin Tony Roy Savarimuthu Presented by Ilusca L. L. Menezes IFT /11/2006

2 Outline Ilusca L. L. Menezes 2

3 Concepts and Definitions: Workflow Workflow Management System Petri Nets Petri net-based workflow modelling Ilusca L. L. Menezes 3

4 Workflow Definition: The automation of a business process, in whole or part, during which documents, information or tasks are passed from one participant to another for action, according to a set of procedural rules. [Workflow Handbook 2002] Ilusca L. L. Menezes 4

5 Workflow A workflow can be described as the flow of information and control in a business process A workflow involves sequences of activities/steps/tasks that describe a business process (Workflow describing the process to manage claim) The term, business process or simply process, is used to relate a workflow [Aalst & Hee 2002] Ilusca L. L. Menezes 5

6 Workflow process definition The workflow process definition specifies which tasks need to be executed and in what order It is useful to identify conditions which correspond to causal dependencies between tasks A condition holds or does not hold (true or false) Each task has pre-conditions and post-conditions (Workflow of a claim) Ilusca L. L. Menezes 6

7 Workflow process definition Cases are handled by executing tasks in a specific order Many cases can be handled by following the same workflow process definition A task which needs to be executed for a specific case is called a work item Most work items are executed by a resource A resource is either a machine (e.g. a printer or a fax) or a person (participant, worker, employee) If a group of resources with similar characteristics is based on the capabilities (i.e. functional requirements) of its members, it is called a role A work item which is being executed by a specific resource is called an activity Ilusca L. L. Menezes 7

8 A three dimensional view of a workflow [Aalst 1998] Ilusca L. L. Menezes 8

9 Why a Workflow? The set of the business processes of a company composes its logical infrastructure After registering and representing the processes, these can be modified and be reorganized to improve the logical infrastructure (Modification of a claim workflow) Ilusca L. L. Menezes 9

10 Workflow Management System Definition: A system that defines, creates and manages the execution of workflows through the use of software, running on one or more workflow engines, which is able to interpret the process definition, interact with workflow participants and, where required, invoke the use of IT tools and applications. [Workflow Handbook 2002] A specific software system, so-called WfMS, controls automated aspects of workflow [Salimifard & Wright 2001] Ilusca L. L. Menezes 10

11 Workflow Management System A WfMS is composed of two main components: The workflow model (process definition) The workflow execution module (workflow enactment service) (Workflow system components and phases [Salimifard & Wright 2001]) Ilusca L. L. Menezes 11

12 Petri nets Originate from the early work of Carl Adam Petri Have a graphical representation Are based on a strong mathematical formalism, which makes it possible to set up mathematical models describing the behaviour of the system The classical Petri nets: Allow for the modeling of states, events, conditions, synchronization, parallelism, choice, and iteration Do not allow for the modeling of data and time [Murata 1989] [Aalst 1998] [Petri 1962] Ilusca L. L. Menezes 12

13 Petri nets Extensions of the basic Petri net model removed these problems: 1970 s: high-level Petri nets 1980 s: hierarchical Petri nets Coloured Petri Nets (also called CP-nets or CPN) is one of the two most well-known dialects of high-level Petri nets CP-nets incorporate both data structuring and hierarchical decomposition - without compromising the qualities of the original Petri nets Ilusca L. L. Menezes 13

14 Petri nets A Petri net is a directed graph consisting of three structural components: places, transitions and arcs Places: Are drawn as circles Represent possible states or conditions of the system Transitions: Are shown by bars or boxes Describe events that may modify system states. Arcs: Tokens: Are the only connectors between a place and a transition in either direction Represent the relationships between places and transitions There is no connection between two nodes of the same type Represent the dynamic behaviour of a system Graphically appear as black dots in places [Salimifard & Wright 2001] Ilusca L. L. Menezes 14

15 Formal definition of CP-nets [Jensen 1994] Ilusca L. L. Menezes 15

16 Petri net-based workflow modelling Zisman (1977) applied Petri nets to model workflow for the first time [Zisman 1997] A Petri net which models a workflow process definition is called a workflow net (WF-net) A WF-net has one input place (i) and one output place (o) All node of the graph should be located on a path from place i to place o Transitions represent tasks Places represent pre- and post-conditions or resources needed for a task to be performed Arcs represent logical relationships between tasks and the flow of the work [Aalst 1998] Ilusca L. L. Menezes 16

17 Routing constructs Sequential: sequential execution of tasks, where one occurs after to another one c1 t1 c2 t2 c3 Parallelism: if one or more tasks can be executed at the same time or in any order AND-split c2 t2 c4 AND-join c1 t1 t4 c6 c3 t3 c5 [Aalst 1998] Ilusca L. L. Menezes 17

18 Routing constructs Conditional: is used to allow for a routing which may vary between cases OR-split OR-join t11 c2 task1 c4 t21 c1 c6 t12 c3 task2 c5 t22 [Aalst 1998] Ilusca L. L. Menezes 18

19 Routing constructs Iteration: repeated execution of a particular task p1 t1 p2 t2 p3 t4 p4 t3 [Aalst 1998] Ilusca L. L. Menezes 19

20 Example Claims Management The process to manage claim shaped in Petri nets [Aalst & Hee 2002] Ilusca L. L. Menezes 20

21 Example Claims Management Tokens have a case identifier which allows for the separation of cases [Aalst & Hee 2002] Ilusca L. L. Menezes 21

22 Example Claims Management The low-level behavior of a task [Aalst & Hee 2002] Ilusca L. L. Menezes 22

23 Overview Background JBees Example Conclusion Ilusca L. L. Menezes 23

24 Overview The authors: Lars Ehrler, Martin Fleurke, Maryam Purvis and Tony Bastin Roy Savarimuthu They present: The architecture JBees Ilusca L. L. Menezes 24

25 The benefit of using a WfMS are: Ability to visualize the overall process and interdependencies between tasks Automation of processes Automated coordination and collaboration between various business entities But, most of the existing WfMS are: Rigid and support only well defined activities specified in advance Centralized architectures which allows single point of failure So, a desirable WfMS should be: Adaptable: in order to accommodate the rapidly changing business environment Ilusca L. L. Menezes 25

26 Background Design approach of WfMS: They use coloured Petri nets (CPN) as workflow process definition formalism and software agents as architectural platform Why coloured Petri nets? Formal notation with a graphical representation Can be used for analysis Can model states and events Why software agents? High level of encapsulation and abstraction Are independent Opportunity to have a flexible system Offer distributed and open platform architecture Ilusca L. L. Menezes 26

27 JBees The architecture: Various collaborating agents that are interacting with each other by following standard agent communication protocols Is based on Opal (Otago Agent Platform) Tools and utilities useful for the development of agent-based systems Uses the CPN execution tool JFern: A CPN simulator and enactment engine to design and execute the models They have modified to support hierarchical models Ilusca L. L. Menezes 27

28 JBees (An overview over the JBees architecture) Ilusca L. L. Menezes 28

29 JBees Adaptability: ManagerA. ProcessAgent startcase() submit new process model() executing case Alt check = true result() check correctness continue with new definition check = false transfer not possible() result() continue with old definition Check correctness: Algorithm based on work of van der Aalst Make sure that the change does not violate the structural and semantic consistency of the model Determine if the transfer is safe or not Ilusca L. L. Menezes 29

30 JBees Reliability: In a WfMS there are usually two central points of failure: 1) Management of resources: Resource Resource - Every resource agent is registered with at least one of the broker agents - If a resource broker is not reachable another broker agent can be contacted ResourceBroker ResourceBroker Resource ResourceBroker Resource Resource Resource 2) Management of persistent data: StorageAgent StorageAgent - Several storage agents, updating each other automatically - If one database agent fails, another one can be contacted Database StorageAgent Database Database Ilusca L. L. Menezes 30

31 JBees Distribution: The process model can be distributed: A process can be divided into multiple sub-processes For each sub process, a new process agent is started These sub-processes can be distributed over different hosts The resource management can be distributed: Even if the process is executed in one location, resource brokers at several locations can be asked for a resource Incorporates an agent-based distributed database: Data can be retrieved/stored by any storage agents When an storage agent detects the change, it synchronizes the distributed database by informing all storage agents to update the data Ilusca L. L. Menezes 31

32 JBees Simulation Has a special simulation agent - a dedicated process agent Monitoring Has a dedicated monitor agent Has integrated the JFreeChart from draw and display graphs Feedback When the controlling agent senses anomalies or violations of a criteria, it sends a warning message to the management agent Ilusca L. L. Menezes 32

33 Example A simple process of ordering a book - Suppose a new order arrives: The process agent puts a job token in the place called Start This activates the transition Order Entry Ilusca L. L. Menezes 33

34 Example The process of allocating a resource and executing a task Ilusca L. L. Menezes 34

35 Example Demonstration of adaptability: Suppose the company changes the way an order is dealt with Ilusca L. L. Menezes 35

36 Example Monitoring: (The percentage utilization of the resources) Ilusca L. L. Menezes 36

37 Example Monitoring: (The waiting time for various tasks in similar cases) Ilusca L. L. Menezes 37

38 Conclusion - Summary They have described the architecture of a prototype agent-based workflow management system: JBees Provides high degree of distribution Deals with various levels of adaptability They showed solutions for the problems arising while implementing JBees has monitoring and feedback mechanisms Future work: They into integrate into JBees one of the existing CPN tools that supports formal analysis so that they can examine the model for certain properties such as reachability Integration of sophisticated resource management Ilusca L. L. Menezes 38

39 Which is the originality of this work? Related Work? Validation of the system? Thank you for your attention! Ilusca L. L. Menezes 39

40 References Fischer, L. ed., Workflow Handbook 2002, Lighthouse Point, Fla.: Future Strategies, Aalst, W. V. P. van der; HEE, V. K. Workflow management: models, methods and systems. Cambridge: MIT Press, Aalst,W.M.P. van der; The application of Petri nets to workflow management. The Journal of Circuits Systems and Computers 8 1, pp , SALIMIFARD, S.; WRIGHT, M. Petri net based modelling of workflow systems: an overview. European Journal of Operational Research, v. 134, p , Petri, C. A.; Kommunikation mit Automaten, Ph.D. Thesis, Universität Bonn, Germany, Murata, T; Petri nets: Properties, analysis and applications, in: Proceedings of the IEEE, vol. 77, pp , Dicesare, F. Harhalakis, G. Proth, J.M. Silva M. and Vernadat F.B. Practice of Petri Nets in Manufacturing, Chapman & Hall, London,1993. ZISMAN, M. D. Representation, specification and automation of office procedures. Ph.D.Thesis University of Pensylvania Wharton School of Business, Pensylvania, K. Jensen: An to the Theoretical Aspects of Coloured Petri Nets. In: J.W. de Bakker, W.-P. de Roever, G. Rozenberg (eds.): A Decade of Concurrency, Lecture Notes in Computer Science vol. 803, Springer-Verlag, , Ilusca L. L. Menezes 40