A Knowledge-Rich Approach to Understanding Text about Aircraft

Systems

Peter ClarkLisbeth Duncan

Heather HolmbackTom Jenkins

John ThompsonBoeing Engineering and Information Technology

Overview• Situation: Using a hand-built, airplane knowledge-base

(KB) at Boeing (e.g., for concept-based search)

• Goal: Extend this KB by processing text:

• from airplane training manuals

• directly from an aerospace engineer

• Target: airplane parts, connections, and behaviors

Challenge• Interpretation of text requires background knowledge

– author trying to convey a model to the reader– only some parts of this are explicitly stated in text– rest is assumed to be already known to the reader

“The hydraulic system supplies power to the

rudder.”

HydraulicSystem Rudder

Supply

Power

Powered-System

Script

Consume Transmit

Conduit

Airplane

source sink

behavior

Approach• Use an aerospace knowledge base (KB):

– Taken from an earlier project and extended– Contains general models about what might be said

• Contains general knowledge of aircraft and systems• Doesn’t know details of specific aircraft

• Text interpretation = specializing and refining this background knowledge

Constraints on the Scope1. Working with restricted sublanguage of English

– Simple, declarative sentences– Regular, “boring” style

“The hydraulic system supplies power to the rudder.”“A ripple damper smooths the pump pressure output.”“The EDP is on the left side of the engine main gearbox.”“The gearbox turns the EDP when the engine turns.”

2. Constrained domain (aircraft systems)– Reduces vocabulary, background KB

3. Domain of mechanical artifacts– Simple statements about structure and behavior

KB

777-200-Airplane

ApproachUser specifies topic (eg. “777-200-Airplane”)

Tail

PoweredSystem

Rudder

VerticalStabilizer

PowerSource

Supplying

FuselageWing

Flap

parts

parts sourcesink script

systems

parts

purpose

connects

agentrecipient

Initial (general) representation of airplane built.

“The hydraulic system supplies

power to the rudder.”

Text is provided.

777-200-Airplane

“The hydraulic system supplies

power to the rudder.”

Tail

PoweredSystem

Rudder

VerticalStabilizer

PowerSource

Supplying

FuselageWing

Flap

KB

parts

parts sourcesink script

systems

parts

purpose

connects

agentrecipient

ApproachThen:1. Text NLP structure

Rudder HydraulicSystem

Supplying

Power

recipient

object

agent

Stage 1

777-200-Airplane

“The hydraulic system supplies

power to the rudder.”

Tail

PoweredSystem

Rudder

VerticalStabilizer

PowerSource

Supplying

FuselageWing

FlapRudder Hydraulic

System

Supplying

Power

KB

?

recipient

object

agent

parts

parts sourcesink script

systems

parts

purpose

connects

agentrecipient

ApproachThen:1. Text NLP structure2. Match NLP structure with airplane repn.

Stage 1 Stage 2

777-200-Airplane

“The hydraulic system supplies

power to the rudder.”

Tail

PoweredSystem

Rudder

VerticalStabilizer

Supplying

FuselageWing

FlapRudder Hydraulic

System

Supplying

Power

KB

HydraulicSystem

Power

ApproachThen:1. Text NLP structure2. Match NLP structure with airplane repn.

Unify the matching structures.

recipient

object

agent

parts

parts sourcesink script

systems

parts

purpose

connects

Stage 1 Stage 2

777-200-Airplane

Tail

PoweredSystem

VerticalStabilizer

FuselageWing

Flap

KB

parts

parts sourcesink script

systems

parts

purpose

connects

Stage 2

The Knowledge Base

Rudder PowerSource

Supplyingagentrecipient

“The hydraulic system supplies

power to the rudder.”

Rudder HydraulicSystem

Supplying

Power

recipient

object

agent

Stage 1

The Knowledge Base• ~500 concepts, ~1500 axioms• Mainly airplane parts, behaviors, and connections• Axioms converted to prototypes (graph structures)

Axiom: “Every airplane has a fuselage, and a tail connected to the fuselage.”

(every Airplane has (parts ((a Fuselage) (a Tail with (connected-to (the Fuselage parts of Self))))

Airplane

Fuselage Tail

parts

connected-to

Prototype (sketch)

Inference: Building the Initial Airplane Representation

777-200-Airplane

Tail

Airplane

Fuselage Tailparts

VerticalStabilizer

HorizontalStabilizer

parts

Flight

Takeoff Cruise Land

Flight

behavior

HorizontalStabilizer

parts

VerticalStabilizer

subevents

Takeoff Cruise Land

Fuselage Tail

parts

connected-to

behavior

Flight

Axioms in KB: Airplane representation:

KB

777-200-Airplane

Tail

PoweredSystem

Rudder

VerticalStabilizer

PowerSource

Supplying

FuselageWing

Flap

parts

parts sourcesink script

systems

parts

purpose

connects

agentrecipient

“The hydraulic system supplies

power to the rudder.”

Stage 1:Text to NLP Structure

777-200-Airplane

“The hydraulic system supplies

power to the rudder.”

Tail

PoweredSystem

VerticalStabilizer

FuselageWing

FlapRudder Hydraulic

System

Supplying

Power

KB

recipient

object

agent

parts

parts sourcesink script

systems

parts

purpose

connects

Stage 1

Stage 1:Text to NLP Structure

Rudder PowerSource

Supplyingagentrecipient

Stage 1: Text to NLP Structure• Superficial linguistic variations normalized • Add initial semantic interpretation

• Commits to: overall parse/syntactic configuration, word senses• May underspecify: some semantic relationships (e.g., modifiers)

Rudder HydraulicSystem

Supplying

Power

recipient

object

agent

Abstract & rewrite

“The hydraulic system supplies

power to the rudder.” Parse &

semantic analysis

Supply_1[sing,pres,3S]

To_5

HydraulicSystem_1

[sing,N]

The_1[det]

delim

recipient

range

object

causer

delim

Power_1[sing,mass]

Rudder_1[sing,N]

The_1[det]

777-200-Airplane

“The hydraulic system supplies

power to the rudder.”

Tail

PoweredSystem

VerticalStabilizer

FuselageWing

FlapRudder Hydraulic

System

Supplying

Power

KB

recipient

object

agent

parts

parts sourcesink script

systems

parts

purpose

connects

Stage 1 Rudder PowerSource

Supplyingagentrecipient

777-200-Airplane

Tail

PoweredSystem

VerticalStabilizer

FuselageWing

Flap

parts

parts sourcesink script

systems

parts

purpose

connects

Rudder PowerSource

Supplyingagentrecipient

“The hydraulic system supplies

power to the rudder.”

Rudder HydraulicSystem

Supplying

Power

recipient

object

agent

Stage 1

?

Stage 2

KBStage 2: Match NLP Structure with Airplane Representation

Stage 2: Match with Airplane Representation• Goal: Integrate text into airplane representation• Approach: find matching (subsuming) structure(s)

Rudder HydraulicSystem

Supplying

Power

recipient

object

agentRudder Power

Source

Supplyingagentrecipient

… ……

Text KB (Topic airplane representation)

Stage 2: Match with Airplane Representation• Goal: Integrate text into airplane representation• Approach: find matching (subsuming) structure(s)• If match found, unify the two structures together

Rudder HydraulicSystem

Supplying

Power

recipient

object

agentRudder Power

Source

Supplyingagentrecipient

… ……

Text KB (Topic airplane representation)

Stage 2: Match with Airplane Representation• Goal: Integrate text into airplane representation• Approach: find matching (subsuming) structure(s)• If match found, unify the two structures together

Rudder HydraulicSystem

Supplying

Power

recipient

object

agentRudder Power

Source

Supplyingagentrecipient

… ……

Rudder HydraulicSystem

Supplyingagentrecipient

…

Power

object

… …

KB expects:

RudderPowerSource

Supplying Power“The hydraulic system supplies power to the rudder.”

But text may deviate with:

RudderHydraulicSystem

Providing Power

“The hydraulic system provides power to the rudder.”

1. Synonyms

RudderHydraulicSystem

Powering

“The hydraulic system powers the rudder.”

2. Contractions

Rudder

HydraulicSystem

Be

Supplier

Power

“The hydraulic system is the supplier of power for the rudder.”

3. Roles

4. …

Matching Problem 1:Linguistic Variation

• Use simple transformation rules to modify NLP structure• No match transform and re-search for a match

RudderHydraulicSystem

Supplying Power

RudderHydraulicSystem

Providing Powersynonym

Rudder

HydraulicSystem

Be

Supplier

Power

role

RudderHydraulicSystem

Powering

contraction/ expansion

Matching Problem 1:Linguistic Variation

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

Explicit facts:

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

“The pilot presses the pedal.”

Explicit facts:

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

“The pilot presses the pedal.”“The pedal pulls a cable.”

Explicit facts:

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

“The pilot presses the pedal.”“The pedal pulls a cable.”“The cable moves the rudder.”

Explicit facts:

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

“The pilot presses the pedal.”“The pedal pulls a cable.”“The cable moves the rudder.”

Explicit facts:

Inference Rule:If A does X, and X causes Ythen add A does Y.

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

“The pilot presses the pedal.”“The pedal pulls a cable.”“The cable moves the rudder.”

Implied facts:

Move

object

agent

instr-ument.

“The pilot moves the rudder using the pedal.”

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

Rudder

Pedal

Pilot

Cable

Press MovePull

Rudder Control System

Script

objectagent behavior

subeventsagent

object agent

object

“The pilot presses the pedal.”“The pedal pulls a cable.”“The cable moves the rudder.”

Implied facts:

Move

object

agent

instr-ument.

“The pilot moves the rudder using the pedal.”

“The pedal moves the rudder using the cable.”

Move

objectinstrument

agent

Matching Problem 2:Expression of Implied Facts

Matching Problem 2:Expression of Implied Facts

• Problem:– Not all airplane facts are explicit in the KB structures– If user refers to an implied fact, matcher will not find it

• Approach:– Match text against an extended version of the KB– Extensions generated on demand

Airplane representation:

Explicit facts

Implied facts

Status and Assumptions• While some components are mature, only complete

throughput for a small number of sentences • Relies on strong expectations from the KB

– Everything that might be said is encompassed by KB• Assumes stage 1 output is correct• Assumes a single model of the airplane is described

Challenges…• Inaccurate knowledge

– “The pump supplies a source of power to the rudder.”• Simplifications/multiple models

– “There are three hydraulic systems in the 777-200.”– “The flight control surfaces steer the airplane.”

• Fluctuating (“fuzzy”) concept boundaries– “hydraulic system” includes controlled devices (eg rudder)?

• Ambiguities not locally resolvable– “The EDP is attached to the airplane’s engine.”

Summary• Goal: extend an airplane KB from text

• Use of background knowledge can help:

– constrains possible interpretations

– provide the surrounding context

• Presented a simple model of how this can be done:

– text interpretation = iterative refinement of a representation

– use of graph matching and unification