January 21-27, 2006, Měřín, Czech Republic

The Knowledge Cartography –A New Approach to Reasoning

over Description Logics Ontologies

Krzysztof Goczyła, Teresa Grabowska, Wojciech Waloszek, Michał Zawadzki

OF=: S EMS 06 :=

#2© 2006 KMG @ GUT

PIPS

KaSeA RDB

Data

Knowledge

Upper layers

KMS

Internet

KaSeA RDB

#3© 2006 KMG @ GUT

Motivations

• PIPS manages knowledge about: – ilnesses,– drugs,– alergies,– diets,– …

• Required data are gathered from many internet sources; the number of information is very large.

#4© 2006 KMG @ GUT

Knowledge Cartography

• Main assumptions:– Terminology is updated so rarely that it might be

considered constant in time.– A knowledge base is queried much more often

than updated (new individual assertions).– A knowledge base should be able to hold and

efficiently process information about large numbers of individuals.

#5© 2006 KMG @ GUT

Knowledge Cartography

• Developed to: – simplify reasoning on numerous objects

(individuals),– simplify storage of inferred results concerning

numerous individuals.

• Processes ontological information in accordance to Description Logics and Semantic Web standard.

#6© 2006 KMG @ GUT

Terminology – an example

• Terminology is described by a set of statements - axioms.

• Suppose, we want to describe the world of people and their pets:– There are no other creatures except People,

Dogs and Cats,– People, Dogs and Cats are disjoint,– Dogs and Cats are CreaturesHavingTails,– People and Cats can be

CreaturesTakingCareOfHygiene.

#7© 2006 KMG @ GUT

Map of concepts

There are no other creatures except People, Dogs and Cats

People Dogs Cats

#8© 2006 KMG @ GUT

Map of concepts

People, Dogs and Cats are disjoint

People Dogs People Cats Cats Dogs

#9© 2006 KMG @ GUT

Map of concepts

Dogs and Cats are CreaturesHavingTails

CreaturesHavingTails Dogs Cats

#10© 2006 KMG @ GUT

Map of concepts

People and Cats can be CreaturesTakingCareOfHygiene

CreaturesTakingCareOfHygiene PeopleCreaturesTakingCareOfHygiene Cats

#11© 2006 KMG @ GUT

Map of concepts

#12© 2006 KMG @ GUT

Map of concepts – signatures

1

2

3

4 5

11000

00001

00111

01000

00010

11111

#13© 2006 KMG @ GUT

Terminological queries

Must every person take care of hygenie?

11000

10011NO

Is a creature without a tail a person?

11000

11000

YES

Is a creature which have a tail and takes care of hygenie a cat?

00100

00110

YES

#14© 2006 KMG @ GUT

Individuals’ signatures

• Individuals’ signatures describe what we know and what we do not know about individuals

Source 1: Fred has a tail

00111

Is Fred a person?

00111

11000NO

Is Fred a dog?

00111

00001MAYBE

#15© 2006 KMG @ GUT

We know something more…Source 2: Fred takes care of hygenie

00111

01100

00100

Is Fred a dog?

00100

00001NO

Is Fred a cat?

00100

00110YES

,

#16© 2006 KMG @ GUT

Restrictions

• Role constructors in the form of R.C and R.C are treated as concepts

• Such constructors must be explicitly defined in ontology.

#17© 2006 KMG @ GUT

Deployment in PIPS

• Cartographic approach has been succesfully deployed in the first release of PIPS system,

• Allowed for achieving short (<1 s) response times for queries in knowledge bases with very large (>10000) number of individuals (sublinear scalability).

#18© 2006 KMG @ GUT

Future work

• Compression of signatures and hierarchical signatures,

• Introducing signatures not only for concepts but also for roles (relations) between individuals.

• Extending expresiveness of KaSeA in order to support complex queries (cardinality constraints, functional, symetric and transitive roles),

#19© 2006 KMG @ GUT

Thank you!

OF=: S EMS 06 :=