Integrating Planning, Execution, and Monitoring ( IPEM) Abrose-Ingerson and Sam Steel

11

Integrating Planning, Integrating Planning, Execution, and MonitoringExecution, and Monitoring

((IPEM) IPEM) Abrose-Ingerson and Sam SteelAbrose-Ingerson and Sam Steel

22

IPEM FrameworkIPEM Framework Set of plan transformations which Set of plan transformations which

remove flaws for the current planremove flaws for the current plan

at each point in execution try to at each point in execution try to transform the current plan into a viable transform the current plan into a viable one (e.g., one that applies in the current one (e.g., one that applies in the current situation to achieve desired goals)situation to achieve desired goals)

33

AssumptionsAssumptions

Current world description (CWD)Current world description (CWD)– can changecan change

actions can fail to achieve purported effectsactions can fail to achieve purported effects actions can have delayed effects (but told when actions can have delayed effects (but told when

actions over “time out”)actions over “time out”)

– CWD may be missing true facts (e.g., sound CWD may be missing true facts (e.g., sound but not complete)but not complete)

44

Chapman TerminologyChapman Terminology

Current plan is incomplete, partialCurrent plan is incomplete, partial– partial commitment on codesignation (assignment partial commitment on codesignation (assignment

of variables to constants)of variables to constants)– partial commitment on ordering of actions partial commitment on ordering of actions

(precedence relations may not cause total order)(precedence relations may not cause total order)– completion of a partial plan P satisfies every completion of a partial plan P satisfies every

constraint in Pconstraint in P

Partial plan P Partial plan P necessarilynecessarily satisfies S if S satisfies S if S holds in every completionholds in every completion

P P possiblypossibly satisfies S if S holds in at least one satisfies S if S holds in at least one completioncompletion

55

A Plan isA Plan is…… BEGIN actionBEGIN action

– postconditions are CWDpostconditions are CWD

END actionEND action– preconditions are desired goalspreconditions are desired goals

set of protections (ranges, causal links)set of protections (ranges, causal links)– connects postondition (supplier) with precondition connects postondition (supplier) with precondition

(user)(user) postcondition and precondition must codesignate (unify)postcondition and precondition must codesignate (unify) supplier necessarily before usersupplier necessarily before user

set of actions (suppliers and users)set of actions (suppliers and users)

66

Sample ProblemSample Problem

Begin

…clear Cclear AA on B

End

A on C

CB

A

D

t.1 t.2 t.3

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Plan GenerationPlan Generation

Also used in modification (incremental Also used in modification (incremental modifications on a partial plan)modifications on a partial plan)– unsupported preconditionunsupported precondition– unresolved conflictunresolved conflict– unexpanded actionunexpanded action

88

Plan Modifications - ReducePlan Modifications - Reduce Unsupported precondition; action A has Unsupported precondition; action A has

precondition P with no range)precondition P with no range)(i.e., no supplier yet)(i.e., no supplier yet)

use an action S already in plan such that S use an action S already in plan such that S possiblypossibly before A and with effect E that before A and with effect E that possiblypossibly codesignates with P codesignates with P– make S necc. before Amake S necc. before A– make E necc. codes. with Pmake E necc. codes. with P

add action to plan that satisfies aboveadd action to plan that satisfies above

99

Sample PlanSample Plan

Begin


Move A from B to C

End

clear zclear xx on y

~clear zclear y~(x on y)x on z A on C

clear Cclear AA on B

~clear Cclear B~(A on B)A on C

Unsupported preconditionadd action

Unsupported preconditionuse exist. act.

1010

Unresolved Conflict - Unresolved Conflict - LinearizeLinearize

IfIf– plan has range R that protects P such thatplan has range R that protects P such that– there is an action A andthere is an action A and

A is possibly after producer of RA is possibly after producer of R A is possibly before consumer of RA is possibly before consumer of R A has an effect which asserts ~P (possibly codes with ~P)A has an effect which asserts ~P (possibly codes with ~P)

– resolve byresolve by A necessarily after consumer of R; orA necessarily after consumer of R; or A necessarily before producer of RA necessarily before producer of R

1111

Example Conflict ResolutionExample Conflict Resolution

Act1:Move D

from C to E

…clear C

act2: Move A

from B to C

Act3:Move C

from F to H

clear C

move act2 after act3

Move act2 before act1



Protect clear C from Act1 to Act3

1212

Unexpanded Action - ExpandUnexpanded Action - Expand

A plan has an action A which is not A plan has an action A which is not primitiveprimitive– resolve by replacing action with its expansion resolve by replacing action with its expansion

(network of activities)(network of activities)

1313

Plan Monitoring & ExecutionPlan Monitoring & Execution

unsupported rangeunsupported range unexecuted actionunexecuted action timed out actiontimed out action unextended rangeunextended range redundant actionredundant action

1414

Unsupported RangeUnsupported Range

Plan has a range (causal link) R which Plan has a range (causal link) R which protects a proposition not in CWDprotects a proposition not in CWD

fixed by removing the rangefixed by removing the range– immediately creates an unsupported immediately creates an unsupported

precondition on consumer (R)precondition on consumer (R)– resolve as in plan generationresolve as in plan generation

1515

Sample PlansSample Plans

Begin


Move A from B to C

End





Suppose we execute this plan but then somehow mistakenly A gets moved from B to D

1616

Sample PlansSample Plans

Begin


Move A from B to D!

End




~clear Dclear B~(A on B) A on D

unsupported rangeremove it!

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Unexecuted Action: ExecuteUnexecuted Action: Execute Action A ready for execution if:Action A ready for execution if:

– A is primitive and is not ENDA is primitive and is not END– all preconditions supported and produced all preconditions supported and produced

by BEGINby BEGIN– it is immediately after an executed actionit is immediately after an executed action– it is not involved in an unresolved conflictit is not involved in an unresolved conflict– there is no “live” action B (i.e., not timed there is no “live” action B (i.e., not timed

out) before A that expects a postcondition out) before A that expects a postcondition that can clobber (threat) any of A’s that can clobber (threat) any of A’s postconditionspostconditions

1818

Executing an Action AExecuting an Action A

Make all parallel actions necessarily after Make all parallel actions necessarily after AA– what about currently executing actions?what about currently executing actions?

Calling associated procedure Calling associated procedure – (actual work)(actual work)

list postconditions as expected list postconditions as expected (monitoring)(monitoring)

recording action as executedrecording action as executed

1919

Unextended Range: ExtendUnextended Range: Extend Can remove a range R and replace it with Can remove a range R and replace it with

R’ whereR’ where R and R’ have the same consumerR and R’ have the same consumer producer of R’ is necessarily before producer of Rproducer of R’ is necessarily before producer of R R’ does not create an unresolved conflict flawR’ does not create an unresolved conflict flaw

special case when activity A executes, special case when activity A executes, achieves desired effect E, range moves achieves desired effect E, range moves from producer=A to producer=BEGINfrom producer=A to producer=BEGIN

seems like an optimizationseems like an optimization

2020

Timed Out Action: Excise ActionTimed Out Action: Excise Action

When an action is terminated and no When an action is terminated and no further effects occurfurther effects occur

presumes that such a time can be presumes that such a time can be specified and that actions can be specified and that actions can be terminatedterminated

remove action and all its ranges from planremove action and all its ranges from plan

2121

Redundant action: Excise ActionRedundant action: Excise Action

An action not producing for any range has a An action not producing for any range has a redundant action flaw and is excisedredundant action flaw and is excised

Excising a redundant action can result in Excising a redundant action can result in further action redundanciesfurther action redundancies

2222

Control: The SchedulerControl: The Scheduler

IPEM maintains an agenda of tasks IPEM maintains an agenda of tasks – each agenda item is a flaweach agenda item is a flaw– with the possible fixeswith the possible fixes

IPEM orders flawsIPEM orders flawsFlaw ordering heuristic•unsupported range•unextended range•timed-out action•unresolved conflict•unsupported precondition•unexpanded action•unexecuted action

Within Flaw Class• select the flaw with fewest options (corresponds to CSP value ordering heuristic)

2323

Example: ReplanningExample: Replanning

Begin


u.2 on t.5clear u.2clear r.1clear r.2...

Move A from B to C

Move u.2from t.5

to r.1

End


~clear zclear y~(x on y)x on z

x on yclear xclear z

x on z~(x on y)clear y~clear z

A on C

u.m on r.n

Initial plan

CBA

Dt.1 t.2 t.3 t.4 t.5 t.6

u.2u.1

r.1

r.2

m=2n=1

x=u.2y=t.5z=r.1

x=Ay=Bz=C

2424


Begin



Move A from B to C

Move u.2from t.5

to r.1

End





A on C

u.m on r.n

CBA

D

t.1 t.2 t.3 t.4 t.5 t.6u.2u.1

r.1

r.2

Baby moves d from t.3 to r.1x=Ay=Bz=C

m=2n=1

x=u.2y=t.5z=r.1

2525


Begin



Move1 A from B to C

Move2 u.2from t.5

to r.2

End





A on C

u.m on r.n

CBA

D

t.1 t.2 t.3 t.4 t.5 t.6u.2u.1

r.1

r.2

Reassign end.n=2 Move2.z=r.2 x=A

y=Bz=C

m=2n=2

x=u.2y=t.5z=r.2

2626


Begin

clear Bclear Cclear AA on BA on u.2


Move1 A from B to C

Move2 u.2from t.5

to r.2

End





A on C

u.m on r.n

CBA

D

t.1 t.2 t.3 t.4 t.5 t.6u.2u.1

r.1

r.2

Baby moves A from B to u.2x=Ay=Bz=C

m=2n=2

x=u.2y=t.5z=r.2

2727


Begin



Move1 A from B to C

Move2 u.2from t.5

to r.2

End





x on z

u.m on r.n

CBA

D

t.1 t.2 t.3 t.4 t.5 t.6u.2u.1

r.1

r.2

Fix lower flawx=Ay=Bz=C

m=2n=2

x=By=t.5z=r.2

2828


Begin



Move1 A from B to C

Move2 u.2from t.5

to r.2

End





x on z

u.m on r.n

CBA

D

t.1 t.2 t.3 t.4 t.5 t.6u.2u.1

r.1

r.2

Fix upper flawx=Ay=u.2z=C

m=2n=2

x=By=t.5z=r.2

2929

Interleaving Planning and ExecutionInterleaving Planning and Execution

BEGINASK

GET meal

END

personlikesthing guest

likesmeal

havemeal

dinnerwith

Sandy

…

DINE

havemeal

dinnerwithguest

…

3030

Interleaving Planning and ExecutionInterleaving Planning and Execution

Begin ASK GET meal END

personlikesthing

guestlikesmeal

havemeal

dinnerwith

Sandy

…

DINE

havemeal

dinnerwithguest

…Sandylikesfondue

3131

DiscussionDiscussion

Enables replanning for “classical Enables replanning for “classical planning”planning”

atomic actions (but parallel execution)atomic actions (but parallel execution) does not enable reasoning about does not enable reasoning about

resources, metric timeresources, metric time

Documents

Integrating Planning, Execution, and Monitoring ( IPEM) Abrose-Ingerson and Sam Steel