Hierarchical Task Network (HTN)
Planning for Grid/Web Services
Composition and Workflow
Austin Tate
AIAI, University of Edinburgh
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
1
Simple Messages
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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.
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Simple extendable underlying “plan” representation from
our work on <I-N-C-A>
– Activities
– Constraints
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Extendable framework from <I-N-C-A> could be useful
– Issues
– Annotations
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Could be complementary component technology in many
other projects described at this workshop
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
2
HTN Planning
Activity Composition
Plan Library
Augment to describe
Grid/web requirements
A2 Refinement
S1
S2
“Initial” Plan
“Final” Plan
A2.1
A2
A2.2
Refine
A4
A1
Augment to describe
Grid/web services
A5
A4
A1
A5
A3
A3
Introduce activities to achieve preconditions
Resolve interactions between conditions and effects
Handle constraints (e.g. world state, resource, spatial, etc.)
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
3
HTN Planning
Initial Plan Stated as “Goals”
Plan Library
Ax Refinement
S1
S2
P
“Initial” Plan
“Refined” Plan
P
Refine
A1.1
A1.2
P&Q
Q
Initial Plan can be any combination of Activities and Constraints
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
4
Relevant AIAI Work to Date
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O-Plan
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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
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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)
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CoAX and CoSAR-TS
– Coalition Command and Control/Search and Rescue Task Support
– Use on CoABS Grid and with KAoS Domain and Policy Management
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
5
O-Plan Unix SysAdmin Aid
O-Plan MOUT Task Description,
Planning and Workflow Aids
O-Plan as a Workflow Planner
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z
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z
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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.
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
8
I-Technology
I-P2
Process
Panels
I-DE
Domain
Editor
Cooperation and
Communication
I-Q
Adaptor
Other
Agents &
Services
CoABS Grid,
KAoS,
AKTBus,
XML Sockets,
Jabber,
[Globus GT3]
I-Plan
Planning
Aid
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
9
<I-N-C-A> Ontology for
Synthesised Artifacts
Issues
Nodes
E.g. activities in a process or parts in a physical artifact
Constraints
Critical 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
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
10
<I-N-C-A>
I
N
C
Issues or Implied
Constraints
Issues
Node
Constraints
(e.g. include activity)
Nodes
Detailed
Constraints
Constraints
A=Annotations
Space of Legitimate Bahaviours
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
11
I-X and <I-N-C-A>
I
Issues or Implied
Constraints
Issues
N
Node
Constraints
Nodes
C
Detailed
Constraints
Constraints
A=Annotations
Space of Legitimate Behaviours
Choose (IH)
Do (IH)
Propagate
Constraints
IH=Issue Handler
(Agent Functional Capability)
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
12
I-X Aim is a Workflow and
Messaging “Catch All”
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Can take ANY requirement to:
–
–
–
–
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Deals with these via:
–
–
–
–
–
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Handle an issue
Perform an activity
Respect a constraint
Note an annotation
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
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Copes with partial knowledge
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
13
CoSAR-TS Demo
Architecture
I-CE and I-K-CE
I-X/KAoS Composer & Enactor
I-Plan
(Planning Service)
Enforcement
(e.g. via KAoS)
Enactment (e.g. via I-P2)
I-CE
Further Information
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http://i-x.info
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http://www.aiai.ed.ac.uk/project/ix
...
coax
...
cosar-ts
...
coakting
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http://www.swsi.org
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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
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z
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
18
Shared Task and Activity Model
User
Role 1
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>).
Other
Agents
User
Role 2
O-Plan
Web
Planner
Artificial Intelligence Applications Institute
Centre for Intelligent Systems and their Applications
19
Version N
Document/
Product Model Refinement Step
Using <I-N-C-A> Framework
of Collaboration
I
N
Document/
Product
Product
Properties
Version N+1
Activity
of Collaboration
Properties
?
Issues
*
Nodes
|
:
C
Constraints
Options
(Alternative
Activities)
Evaluations
~
+ - =
Make Choice
Record Rationale
Preferences
#
A
“
Annotation,
Statements,
Arguments,
Reports
Evaluation
Criteria
Options for the Activity to be performed may be
evaluated against evaluation criteria. The result of
evaluations may be a Pro (+), Con (-), or neutral (=).