agent workflows with wade

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The workflowmetaphor

Agent-basedworkflows

WADEOverview

Architecture

The Factorialcase studyGeneral Information

Implementation

Preparing theInfrastructure

Creating the Agent

Creating theWorkflow

WADE DelegationModel

Runningsub-workflows

Agent Workflows with WADE

Márcio Fuckner1

1Université de Technologie de Compiègne, France

Multiagent System Development

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Outline

1 The workflow metaphor

2 Agent-based workflows

3 WADEOverviewArchitecture

4 The Factorial case studyPreparing the InfrastructureCreating the AgentCreating the WorkflowWADE Delegation ModelRunning sub-workflows

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Definition

WorkflowA workflow is the automation of a businessprocess, which artifacts, information and/or tasksare passed from one actor to another accordingto a set of procedural rules.[Workflow Management Coalition, 2013]

FormalismsMany formalisms exist to represent a workflow.Some examples are flow charts, UML activitydiagrams and finite state machine diagrams.

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A workflow example

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Functional Areas

Figure: Source: [Caire, 2008]

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Examples of Workflow DescriptionLanguages

BPELBusiness Process Execution Language.

• Keywords: SOA, WS oriented• More information: OASIS

(http://www.oasis-open.org)

XPDLXML Process Definition Language.

• Keywords: Visual modelling notations,XML based

• More information: Workflow ManagementCoalition (http://www.wfmc.org)

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Pros and Cons

Pros

• Extremely intuitive. Can be validated bydomain experts with no programming skills

• Self-documented• Execution steps are made explicit• Workflows are interpreted at runtime• Several infrastructure facilities

Cons

• Not suitable to deal with low-leveloperations

• Supporting tools not comparable with thoseavailable for normal code development

• Less efficient execution

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Bringing the workflow approach to theMultiagent world

Agent-based workflowsThe basic idea is to use theexpressiveness of the workflowmetaphor to improve the agentcommunication process.

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What is WADE?

• is a software platforma based on JADE• A WADE application is also a JADE application• All JADE features are available in WADE too

• Allows the execution of tasks using the workflowmetaphor

• Adopted the XPDL meta-model to facilitateimport/export from/to a standard workflowrepresentation format

aFor more information: http://jade.tilab.com/wade/

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Main components

Figure: Source: [Telecom Italia, 2011b]

WADE and WOLFIn principle WADE supports“notepad-programming”, but it comeswith a graphical developmentenvironment called WOLF[Telecom Italia, 2011b].

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Architecture


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A classroom case study using WADE

• Now, it’s time to develop asimple but complete applicationusing WADE ...

• ... from scratch !

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Formal Definition

• In mathematics, the factorial ofa non-negative integer n,denoted by n!, is the product ofall positive integers less than orequal n

• For example: 5! = 5 x 4 x 3 x 2x 1 = 120

• According to the rule, the valueof 0! is 1

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Implementing the application using theworkflow metaphor

NoteWe know ... The factorial problem could easily be implemented in one line, as theexample above in LISP:

(defun fa (n)(cond ((eq n 1) n) ((> n 1) (* (fa (- n 1) ) n ) ) )

By the other hand, this problem allows to explore the workflow metaphor, keepingus focused on the approach and not on out-of-scope issues.

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Implementing the application using theworkflow metaphor

• We will start by implementing asimple solution using only oneworkflow agent

• Next, we will improve theapplication, enabling theparallel execution ofsub-workflows

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A workflow with only one actor

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Creating the Project

• (1) Creating a JavaProject

• Adding WADE Nature

• Configuring WADE

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• Creating a Java Project

• (2) Adding WADENature

• Configuring WADE

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• Creating a Java Project

• Adding WADE Nature

• (3) Configuring WADE

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WADE distribution structure

Figure: Source: [Caire, 2008]

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Application Structure

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(4) Defining the Agent

• The Factorial Agent willnot inherit from thejade.core.Agent classdirectly

• We will use theWorkflowEngineAgent a

• All workflow agents areautomatically registeredin the DF

aSee FactorialAgent.java

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(5) Agent Types

• WADE agentsautomatically registerswith the DF providing adefault description.

• Such descriptioncontains the agent typeas indicated in thecfg/types.xml file whererelevant agent types aredeclared.

Figure: See cfg/types.xml

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(6) Allowing the Agent to executeWorkflows

DispatchCapabilities ObjectBy embedding a DispatchingCapabilitiesinstance, an agent acquires the ability oflaunching workflows, setting andretrieving, workflow relevant data andlistening to events generated by theexecution of workflows[Telecom Italia, 2011a].

Figure: See FactorialAgent.java

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(7) Preparing the configuration for thefirst execution

Configuration fileBefore lauching our applicationwe still need to declare whichagents we want to activate in it.This can be done by means ofan "Application ConfigurationFile".

Figure: See cfg/configuration/Factorial.xml

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Running the application for the firsttime

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Basic workflow terminology

• Workflow/Process

• Activity

• Transition

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The WADE meta-model


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In practice


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(8) Creating a Workflow

• Workflows inWADE are Javaclasses that extendtheWorkflowBehaviourclass

• Indirectly, this classextends our knownJADE Behaviour

• WOLF provides aview to edit aworkflow in abidirectionalfashion.

Figure: See FactorialWorkflow.java

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(9) (10) Executing Workflows

Figure: See calculate method defined in FactorialAgent.java

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Running the application

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WADE Delegation Model


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A workflow with two actors

Executing sub-workflowsNow, we will change the codeto allow agents delegate theexecution of sub-workflows toother agents

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Application Structure

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Changing Project Settings

• (11) Creating the multiply agent (SeeMultiplyAgent.java)

• Adding multiplier to cfg/types.xml

• Creating the multiplication sub-workflow (SeeMultiplyWorkflow.java)

• Changing the project configuration See cfg/configuration/Factorial.xml)

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• Creating the mutiply agent (See MultiplyAgent.java)

• (12) Adding multiplier to cfg/types.xml



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• (13) Creating the multiplication sub-workflow (SeeMultiplyWorkflow.java)


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• (14) Changing the project configuration (Seecfg/configuration/Factorial.xml)

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(15) Changing the Factorial Agent

Executing sub-workflowsNow, we will change the codeto allow the factorial agentkeep on track of multiplyagents life-cycle a.

aSee subscribe method defined in FactorialAgent.java

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(16) Changing the Factorial Workflow

Changing the workflowNow, we will change theworkflow in order to executethe multiplication in parallel,joining the results at the endof all operations a.

aSee FactorialWorkflow.java

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Running the application

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Conclusion

Questions?

• A hands-on example on WADE• Much more examples and resources on

http://jade.tilab.com/wade/• See also the WADE tutorial at

http://jade.tilab.com/wade/doc/tutorial/WADE-Tutorial.pdf

Contact Information

• Marcio Fuckner• [email protected]

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Caire, G. (2008).WADE: an open source platform for workflows and agents.The Seventh International Conference On AutonomousAgents and Multiagent Systems.

Telecom Italia (2011a).WADE Tutorial.Telecom Italia.Available athttp://jade.tilab.com/wade/doc/tutorial/WADE-Tutorial.pdf.

Telecom Italia (2011b).WADE User Guide.Telecom Italia.Available athttp://jade.tilab.com/wade/doc/WADE-User-Guide.pdf.

Workflow Management Coalition (2013).

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Workflow Management Coalition Terminology and Glossary.Workflow Management Coalition.Available at http://www.wfmc.org.

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