Hierarchical Task Network (HTN) Planning for Grid/Web Services Composition and Workflow

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Artificial Intelligence Applications InstituteCentre for Intelligent Systems and their Applications

Hierarchical Task Network (HTN)Planning for Grid/Web Services

Composition and Workflow

Austin TateAIAI, University of Edinburgh

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Simple MessagesSimple Messages

HTN Planning could be a useful paradigm– Compose workflows from requirements and component/template libraries– Covers simple through to very complex (pre-planned) components– Allows for execution support, reactive repair, recovery, etc.

Simple extendable underlying “plan” representation from our work on <I-N-C-A>

– Activities– Constraints

Extendable framework from <I-N-C-A> could be useful– Issues– Annotations

Could be complementary component technology in many other projects described at this workshop

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HTN PlanningHTN PlanningActivity CompositionActivity Composition

A1

A2

A3

A5A4

“Initial” Plan

Refine

Introduce activities to achieve preconditionsResolve interactions between conditions and effects

Handle constraints (e.g. world state, resource, spatial, etc.)

“Final” Plan

A2.2A2.1

A1

A3

A5A4

Plan Library

A2 Refinement

S2S1

Augment to describeGrid/web services

Augment to describeGrid/web requirements

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HTN PlanningHTN PlanningInitial Plan Stated as “Goals”Initial Plan Stated as “Goals”

Refine

Plan Library

Ax Refinement

S2S1

P

“Initial” Plan

P & Q

Initial Plan can be any combination of Activities and Constraints

“Refined” Plan

A1.2A1.1

Q

P

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Relevant AIAI Work to DateRelevant AIAI Work to Date O-Plan

– On-line web service exposing API via CGI scripts since 1994– HTTP interface since 1997– Simple - single user single-shot plan generator– More comprehensive - multiple users with multiple roles, long transactions,

collaborative planning, execution and plan repair on failure– Air Campaign Planning Workflow Aid - people and systems

I-X– I-X supports the construction of mixed-initiative agents and systems which are

intelligible to their users and to other systems and agents– Dynamic workflow generation and reactive execution support– I-Q query adaptor for OWL, OWL-S lookups via CMU Matchmaker, Semantic

Web Queries via RDF, DAML, OWL and RDQL (AKTive Portal)– I-Plan planning aid (to be packaged as a web service composition tool)

CoAX and CoSAR-TS– Coalition Command and Control/Search and Rescue Task Support– Use on CoABS Grid and with KAoS Domain and Policy Management

O-Plan Unix SysAdmin AidO-Plan Unix SysAdmin Aid

O-Plan MOUT Task Description,O-Plan MOUT Task Description,Planning and Workflow AidsPlanning and Workflow Aids

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O-Plan as a Workflow PlannerO-Plan as a Workflow Planner

Air Campaign Planning (ACP) Workflow – 1996 Real ACP Process Models utilised Composes workflow Process from a range of

system and user capability descriptions Models the creation and modification of

“Process Products” by effects and conditions on process steps. Values of attributes of each product/object changed during process. E.g. status of documents.

Supports planning, execution monitoring and plan repair on failure.

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I-TechnologyI-Technology

Cooperation and Communication

I-DEDomainEditor

I-P2

ProcessPanels

I-PlanPlanningAid

CoABS Grid,KAoS,

AKTBus,XML Sockets,

Jabber,[Globus GT3]

Other Agents &Services

I-Q Adaptor

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<I-N-C-A> Ontology for <I-N-C-A> Ontology for Synthesised ArtifactsSynthesised Artifacts

Issues

Nodes E.g. activities in a process or parts in a physical artifact

ConstraintsCritical Constraints (shared across multiple components)Auxiliary Constraints (localised to a single component)

Annotations E.g. decision rationale and other notes

Used for Processes and Process Products

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<I-N-C-A><I-N-C-A>

Constraints

Issues

Nodes

Space of Legitimate Bahaviours

Issues or ImpliedConstraints

NodeConstraints

(e.g. include activity)

DetailedConstraints

I

N

C

A=Annotations

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Constraints

Issues

Nodes

Space of Legitimate Behaviours

Issues or ImpliedConstraints

NodeConstraints

DetailedConstraints

I

N

C

A=Annotations

I-X and <I-N-C-A>I-X and <I-N-C-A>

Do (IH)

Choose (IH)

IH=Issue Handler (Agent Functional Capability)

PropagateConstraints

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I-X Aim is a Workflow and I-X Aim is a Workflow and Messaging “Catch All”Messaging “Catch All”

Can take ANY requirement to:– Handle an issue– Perform an activity– Respect a constraint– Note an annotation

Deals with these via:– Manual activity– Internal capabilities– External capabilities– Reroute or delegate to other panels or agents– Plan and execute a composite of these capabilities

Receives reports and interprets them to:– Understand current status of issues, activities and constraints– Understand current world state, especially status of process products– Help user control the situation

Copes with partial knowledge

CoSAR-TS Demo CoSAR-TS Demo ArchitectureArchitecture

I-Plan(Planning Service)

I-CE and I-K-CEI-CE and I-K-CEI-X/KAoS Composer & EnactorI-X/KAoS Composer & Enactor

I-CEI-CE

Enactment (e.g. via I-P2)Enactment (e.g. via I-P2)

EnforcementEnforcement (e.g. via KAoS)(e.g. via KAoS)

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http://i-x.info

http://www.aiai.ed.ac.uk/project/ix . . . coax . . . cosar-ts . . . coakting

http://www.swsi.org

Thanks to my co-workers on the I-X and CoSAR-TS projects:– Jeff Dalton, Stephen Potter, Stuart Aitken, Jessica Chen-Burger,

John Levine, Natasha Lino, Clauirton Siebra– IHMC: Jeff Bradshaw, Andrzej Uszok

Further InformationFurther Information

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Shared Task Model – Mixed initiative model of “mutually constraining the space of products”.

Shared Space of Options – for the product.Shared Model of Agent Capabilities -

handlers for issues, functional capabilities and constraint managers.

Shared Understanding of Authority – management of the authority to handle issues and act which may take into account options.

Shared Product Model – using constraints on the space of products (<I-N-CA>).

Shared Task and Activity ModelShared Task and Activity Model

UserRole 1

O-PlanWebPlanner

Other Agents

UserRole 2

*

Nodes

:

Constraints

~

Preferences

|

Options (Alternative Activities)

Evaluations

+ - =

#

Evaluation Criteria

Activity

Record RationaleMake Choice

“Annotation,Statements,Arguments,Reports

?

Issues

Version N

Document/

Product

of Collaboration

Properties

N

I

C

AOptions for the Activity to be performed may beevaluated against evaluation criteria. The result ofevaluations may be a Pro (+), Con (-), or neutral (=).

Document/

Product

of Collaboration

Version N+1

Properties

Product Model Refinement StepProduct Model Refinement StepUsing <I-N-C-A> FrameworkUsing <I-N-C-A> Framework

Documents

Hierarchical Task Network (HTN) Planning for Grid/Web Services Composition and Workflow