04/19/23 Gio Wiederhold SKC RKF 1

.

Tools For Resolving Heterogeneityin Ontologies

SKC ProjectComputer Science Department

Stanford UniversityGio Wiederhold, PI

04/19/23 Gio Wiederhold SKC RKF 2

Problem Addressed by SKCOntologies come from many autonomous sources• Differing viewpoints (by source)

– differing coverage vehicles (DMV, AIA)

– differing granularity trucks (shipper, manuf.)

– differing terms for similar items { lorry, truck }

– same terms for dissimilar items trunk(luggage, car)

• Created by focused groups– high quality used in commerce

– ongoing maintenance annual models

• Poor precision when merged

ok for web browsing , poor for business

04/19/23 Gio Wiederhold SKC RKF 3

Domains and Consistency .

• a domain will contain many objects

• the object configuration is consistent

• within a domain all terms are consistent &

• relationships among objects are consistent

• context is implicit

No committee is needed to forge compromises * within a domain

Compromises hide valuable details

Domain Ontology

04/19/23 Gio Wiederhold SKC RKF 4

Heterogeneity among Domains

If interoperation involves distinct

domains mismatch ensues

• Autonomy conflicts with consistency, – Local Needs have Priority,

– Outside uses are a Byproduct

Heterogeneity must be addressed

• Platform and Operating Systems

• Representation and Access Conventions • Naming and Ontology

04/19/23 Gio Wiederhold SKC RKF 5

SKC Objective

Provide for Maintainable Ontologies

• devolve maintenance onto many domain-specific experts / authorities

• provide an algebra to compute composed ontologies that are limited to their articulation terms

• enable interpretation within the source contexts

SKC

04/19/23 Gio Wiederhold SKC RKF 6

An Ontology Algebra

A knowledge-based algebra for ontologies

The Articulation Ontology (AO) consists of matching rules that link domain ontologies

Intersection create a subset ontology keep sharable entries

Union create a joint ontology merge entries

Difference create a distinct ontology remove shared entries

04/19/23 Gio Wiederhold SKC RKF 7

Sample Operation: INTERSECTION

Source Domain 1:Owned and maintained by Store

Result contains shared terms,useful for purchasing

Source Domain 2:Owned and maintainedby Factory

Articulation

04/19/23 Gio Wiederhold SKC RKF 8

Tools to create articulations

Graph matcherforArticulation- creatingExpert

Vehicle ontology

Transport ontology

Suggestionsfor articulations

04/19/23 Gio Wiederhold SKC RKF 9

continue from initial point

Also suggest similar terms for further articulation:

• by spelling similarity,• by graph position• by term match repository

Expert response:1. Okay2. False3. Irrelevant to this articulation

All results are recorded

Okay’s are converted into articulation rules

04/19/23 Gio Wiederhold SKC RKF 10

Candidate Match Repository

Term linkages automatically extracted from 1912 Webster’s dictionary *

* free, other sources . being processed.

Based on processing headwords definitions using algebra primitives

Notice presence of 2 domains: chemistry, transport

04/19/23 Gio Wiederhold SKC RKF 11

Using the Match Repository

04/19/23 Gio Wiederhold SKC RKF 12

Using the Match Repository

04/19/23 Gio Wiederhold SKC RKF 13

if [base_station.receiving] = true then satellite_data = [base_station] satellite_data.timestamp = now

if [satellite_data.age] < 24 hours or [radio_jamming.level] > 30% then recon_data = [satellite_data]except when [flight_data.age] < 1 hour or [rain_sensor.daytotal] > 1 inch then recon_data = [flight_data]

assert [recon_data]

Rules for Real-Time Data

04/19/23 Gio Wiederhold SKC RKF 14

INTERSECTION support

Store Ontology

Articulation ontology

Matching rules that use terms from the 2 source domains

Factory Ontology

Terms usefulfor purchasing

04/19/23 Gio Wiederhold SKC RKF 15

Other Basic Operations

typically priorintersections

UNION: mergingentire ontologies

DIFFERENCE: materialfully under local control

Arti-culation ontology

04/19/23 Gio Wiederhold SKC RKF 16

Features of an algebra

Operations can be composed

Operations can be rearranged

Alternate arrangements can be evaluated

Optimization is enabled

The record of past operations can be

kept and reused when sources change

04/19/23 Gio Wiederhold SKC RKF 17

Articulationknowledgefor U

U

U

(A B)U

(B C)U

(C E)

Knowledge Composition

Knowledge resource

B

Knowledge resource

A

Knowledge resource

C

Knowledge resource

D

U

(C D)

U

(B C)

Articulationknowledge

Composed knowledge forapplications using A,B,C,E

Knowledge resource

E

U

(C E)

Legend:

U : union

U

: intersection

Articulationknowledgefor (A B)

U

04/19/23 Gio Wiederhold SKC RKF 18

Primitive Operations

Unary

• Summarize -- abstract • Glossarize - list terms

• Filter - reduce instances

• Extract - move into context

Binary • Match - data corrobaration

• Difference - distance measure

• Intersect - use of articulation

• Union - search broadening

Constructors• create object• create setConnectors• match object• match setEditors• insert value• edit value• move value• delete valueConverters• object - value• object indirection• reference indirection

Model and Instance

04/19/23 Gio Wiederhold SKC RKF 19

Exploiting the result .

Processing & query evaluation is best performed withinSource Domains & by their engines

Result has linksto source

Avoid n2 problem of interpretermapping [Swartout HPKB year 1]

04/19/23 Gio Wiederhold SKC RKF 20

Sample Processing in HPKB

• What is the most recent year an OPEC member nation was on the UN security council?

– Related to DARPA HPKB Challenge

Problem

– SKC resolves 3 Sources» CIA Factbook ‘96

(nation)

» OPEC (members, dates)

» UN (SC members, years)

– SKC obtains the Correct Answer

» 1996 (Indonesia)

– Problems resolved by SKC* Factbook has out of date

OPEC & UN SC lists

• Indonesia not listed

• Gabon (left OPEC 1994)

* different country names

• Gambia => The Gambia

* historical country names

• Yugoslavia

» UN lists future security council members

• Gabon 1999

» intent of original question

• Temporal variants

04/19/23 Gio Wiederhold SKC RKF 21

Domain Specialization .

• Knowledge Acquisition (20% effort) &

• Knowledge Maintenance (80% effort *)

to be performed

• Domain specialists

• Professional organizations

• Field teams

of modest size

Empowermentautomouslymaintainable

* based on experience with software