An introduction to topic maps,ontologies and published subjects

http://www.ontopia.net/

© 2003 Ontopia AS 1

The TAO of Topic Maps

An Introduction toTopic Maps,Ontologies, andPublished Subjects

Steve Pepper, CEO, OntopiaConvenor ISO/IEC JTC 1/SC 34/WG 3Editor XML Topic Maps<[email protected]>



Who am I?

• Steve Pepper– Norway’s Head of Delegation to ISO SC34– Convenor of ISO/IEC JTC 1/SC 34/WG 3 (Information Association)– Editor of XML Topic Maps 1.0 specification (XTM)– Editor of Topic Map Constraint Language– Founder and CEO of Ontopia

• Ontopia– The Topic Map Company– Specialists in Topic Map Software and Services– Norwegian company, headquartered in Oslo



What are Topic Maps?

• An international standard, approved by the ISO

• A form of knowledge representation that is optimized for information management

• A formal data model with an XML interchange syntax

• An indexing and navigation paradigm for humans

• A source of intelligent data for software agents

• A technology for exploiting ontologies



Introducing the Topic Map Model

• The core concepts of Topic Maps are based on those of the back-of-book index

• The same basic concepts have been extended and generalized for use with digital information

• Envisage a 2-layer data model consisting of– a set of information resources (below), and– a “knowledge map” (above)

• This is like the division of a bookinto content and index knowledge layer

information layer

(index)

(content)



(1) The Information Layer

• The lower layer contains the content– usually digital, but need not be– can be in any format or notation– can be text, graphics, video, audio, etc.

• This is like the content of the book to which theback-of-book index belongs

information layer



(2) The Knowledge Layer

• The upper layer consists of topics and associations– Topics represent the subjects that the information is about

• Like the list of topics that forms a back-of-book index

– Associations represent relationships between those subjects• Like “see also” relationships in a back-of-book index

knowledge layer

composed by

born in

composed by

Puccini

Tosca

Lucca

MadameButterfly



Linking the Layers Through Occurrences

• The two layers are linked together

– Occurrences are information resources that are pertinentto a given knowledge topic

– The links (or locators) arelike page numbers in aback-of-book index

Puccini

Tosca

Lucca

composed by

born in

composed by

MadameButterfly

knowledge layerinformation layer



Summary of Core Topic Maps Concepts

• A pool of information or data– any type or format

• A knowledge layer, consisting of:


• Associations– expressing relationships between

knowledge topics

composed by

born in

composed by

• Occurrences– information that is relevant in some

way to a given knowledge topic

• = The TAO of Topic Maps

• Topics– a set of knowledge topics for the

domain in questionPuccini

Tosca

Lucca

MadameButterfly



Topic Maps and Back-of-Book Indexes

Cavalleria Rusticana, 71, 203-204Mascagni, Pietro Cavalleria Rusticana, 71, 203-204Rustic Chivalry, see Cavalleria Rusticanasingers, 39-52 See also individual names baritone, 46 bass, 46-47 soprano, 41-42, 337 tenor, 44-45

+ other conventions

(composer)

n occurrences (and types)topics with multiple namesassociations (and types)

+ multiple indexes

• Index of names• Index of places• Index of subjects

topics (and types)

Basic concepts:



Topic Maps and Ontologies

• The basic building blocks are– Topics: e.g. “Puccini”, “Lucca”, “Tosca”– Associations: e.g. “Puccini was born in Lucca”– Occurrences: e.g. “http://www.opera.net/puccini/bio.html is a biography of Puccini”

• Each of these constructs can be typed– Topic types: “composer”, “city”, “opera”– Association types: “born in”, “composed by”– Occurrence types: “biography”, “street map”, “synopsis”

• All such types are also topics (within the same topic map)– “Puccini” is a topic of type “composer” … and “composer” is also a topic

• A topic map thus contains its own ontology– (“Ontology” is here defined as the classes of things that exist in the domain…)

Demo of the Omnigator



The Omnigator

A free topic map browser and debuggerOnline demo: http://www.ontopia.net/omnigator

Download: http://www.ontopia.net/download/freedownload.html



The Omnigator: A Generic Topic Map Browser

• An Omnivorous Topic Map Navigator– The Omnigator will Eat Anything (provided it’s a topic map!)– Any Ontology: including your own– Just drop your own topic map into the Omnigator directory

and away you go!– The Omnigator makes “reasonable sense” out of any

“reasonably sensible” topic map

• And it's Free!– Download it from the Ontopia web site

• http://www.ontopia.net– Or view it online at

• http://www.ontopia.net/omnigator



How the Omnigator Works

J2EE Web Servere.g. Tomcat

Omnigator

Ontopia TopicMap Engine

topicmap

<HTML>pages

http

server client

http://www.ontopia.net/omnigator

current topic

(multiple) names

(multiple) types

multipleoccurrences

multipleassociations

http://www.ontopia.net/omnigator



With this Simple but Flexible Model You Can• Make knowledge explicit, by

– Identifying the subjects that your information is about– Expressing the relationships between those subjects

• Bridge the domains of knowledge and information, by– Describing where to find information about the subjects– Linking information about a common subject across multiple repositories

• Transcend simple categories, hierarchies, and taxonomies, by– Applying rich associative structures that capture the complexity of knowledge

• Enable implicit knowledge to be made explicit, by– Providing clearly identifiable hooks for attaching implicit knowledge

• But there’s more (of course)…



Supporting Context through Scope

• Topic Maps are about representing knowledge

• Knowledge is not absolute; it has a contextual aspect

• Context sensitivity is handled through the concept of scope

• Scope makes it possible to– Cater for the subjectivity of knowledge– Express multiple viewpoints in one knowledge base– Provide personalized views for different groups of users– Track the source of knowledge during merging

• (Scopes are defined as sets of topics)



How Scope Works

• Topics have “characteristics”– Its names and occurrences, and the roles it

plays in associations with other topics

• Every characteristic is valid within some context (scope), e.g.

– the name “Ruotsi” for the topicSweden in the scope “Finnish”

– a certain information occurrencein the scope “technician”

– a given association is true in thescope (according to) “Authority X”

name

occurrence

association roleassociation role

name

occurrence

association role

nameTT

name

occurrence

association role

nameT

Filtering by scope



Applications of Scope

• Multiple world views– Reality is ambiguous and knowledge has a subjective dimension– Scope allows the expression of multiple perspectives in a single Topic Map

• Contextual knowledge– Some knowledge is only valid in a certain context, and not valid otherwise– Scope enables the expression of contextual validity

• Traceable knowledge aggregation– When the source of knowledge is as important as the knowledge itself:– Scope allows retention of knowledge about the source of knowledge

• Personalized knowledge– Different users have different knowledge requirements– Scope permits personalization based on personal references, skill levels,

security clearance, etc.

Demo of scope and filtering in the Omnigator



How Topic Maps Improve Access to Information• Intuitive navigational interfaces for humans

– The topic/association layer mirrors the way people think

• Powerful semantic queries for applications– A formal underlying data structure– Demo of querying in the Omnigator

• Customized views based on individual requirements– Personalization based on scope

• Information aggregation “sans frontiers”– Topic Maps can be merged automatically…– Demo of merging in the Omnigator



Principles of Merging in Topic Maps

• In Topic Maps, every topic represents some subject

• The collocation objective requires exactly one topic per subject– When two topic maps are merged, topics that represent the

same subject should be merged to a single topic– When two topics are merged, the resulting topic has the

union of the characteristics of the two original topics

name

occurrence

association role

T

association role

name

occurrence

association role

name

A second topic (in another topic map) “about” the same subject

TMerge the two topics together...Merge the two topics together...

...and the resulting topic has the unionof the original characteristics

name

occurrence

association role

nameT

Det uunngåelige Ibsen-eksempelet

SNL

SNL

SNL

SNL

Skienkom-mune

CapLex

CapLex

NBL

Henrik Ibsen

Hedda Gabler

Skien

Et dukkehjemA doll’s house

skrev

født i

skrev

“virkelighet”

emnekart

informasjon

kunnskap

Ibsen-senter

Ibsen-senter

Ibsen-senter

Ibsen-senter

Ibsen-senter

Ibsen-senter

Et dukkehjemHelmerHelmer

Dr. RankDr. RankFru LindeFru Linde

KrogstadKrogstadNoraNora



Applications of Merging

• Information integration– Information that spans multiple repositories can be merged to provide a unified view of

the whole

• Knowledge sharing across the organization– Knowledge captured in one part of an organization can be made available to the whole

organization

• Distributed knowledge management– There is no need to centralize knowledge management in order to make it sharable

• Knowledge sharing between organizations– Information and knowledge can be shared without enforcing a common vocabulary



Integrating Information Across Systems

• Topic Maps are designed for ease of merging!– Multiple Topic Maps can be created from many different repositories of

information ... and then merged to provide a unified view of the whole

• Typical Applications:– Integration of hitherto disconnected “islands” of information within an enterprise– Federation of knowledge

from multiple sources

• Advantages:– Consolidated access to

all related information– Does not require

migration of existingcontent

KnowledgeSpace

InformationSpace

Order2

CustomerA

Order1

CustomerB

ProductX

ProductZ

SkillQ

ProductY

owns

orders

orders

contains

contains

containsintegrates

integrates

requires

Customerdatabase

Orderdatabase

Productdatabase

Skillsdatabase

Customerdatabase



What Makes Merging Possible?

• NOT the use of names, which are notoriously unreliable– Names are not unambiguous

• (the homonym problem)– Many topics have multiple names

• (the synonym problem)

• Reliable knowledge aggregation is only possible through the use of unique global identifiers

• The issue of identification of subjects is crucial– If subjects have unique identifiers, people can be free to use whatever

names they like – and machines can still aggregate information



COMPUTERDOMAIN

The Crucial Concept of Subject Identification• Topics exist in order to allow

us to discourse about subjects

• It is crucially important to be able to establish exactly which subject a topic represents, i.e. to establish its subject identity

– Without the ability to know when applications are talking about the same thing, there can be no interoperability

• The most prevalent method of establishing identity in today’s networked environments is to use URIs

“REALITY”


composed by

born in

composed by

Puccini

Tosca

Lucca

MadameButterfly



Using URIs to Identify Resources



Addressable and Non-addressable Subjects

• URIs are the addresses of resources

• They work fine when subject is a resource (e.g. a document)– It exists somewhere within the computer system, has a location, and can

therefore be “addressed”• For example, this presentation might be located at

http://www.ontopia.net/tutorials/tm-intro.ppt– The address of an addressable subject is sufficient to unambiguo establish the

subject’s identity– This is called the subject address

• But most subjects are not information resources– Puccini, Lucca, Tosca, Madame Butterfly, love, darkness, French, …– These all exist outside the computer domain and cannot be addressed directly



Life, the Universe and Everything

The Computer Domain

The Topic Map Domain

Subject Indicators

• The identity of non-addressable subjects is established indirectly

– Through an information resource (like a definition or a picture) that provides some kind of indication of the subject’s identity to a human

– Such a resource is called asubject indicator

– A topic may have multiple subject indicators

• Because it is a resource, a subject indicator has an address, even though the subject that it is indicating does not

– Computers can use the address of the subject indicator to establish identity

– These are called subject identifiers– Subject indicators and subject identifiers

are the two sides of the human-computer dichotomy

subject

Giacomo Puccini, Italian composer, b. Lucca 22nd Dec 1858, d. Brussels, 29th Nov 1924. Best known for his operas, of which Tosca is the most . . .

subject indicator

Puccini

http://p

si.ontopia.

net/o

pera/pucc

ini.htm

l

subject identifier

topichttp://

www.ontopia.net/© 2002 Ontopia AS



Published Subjects

• A subject indicator that has been made available for use outside one particular application is called a published subject indicator (PSI)

– Anyone can publish PSI sets– Adoption of PSI sets will be an evolutionary process that will lead to greater and

greater interoperability – between topic map applications, between topic maps and RDF, and across the Semantic Web in general

– Publishers and users of ontologies may be among the greatest beneficiaries

• OASIS technical committees– pubsubj: http://www.oasis-open.org/committees/tm-pubsubj/

• Guidelines for publishing PSI sets– geolang: http://www.oasis-open.org/committees/geolang/

• A PSI set for geographical and language subjects• Based on existing standards (e.g. ISO 639, ISO 3166)

– xmlvoc: http://www.oasis-open.org/committees/xmlvoc/• A PSI set for an ontology of XML and related standards



Using URIs to Identify Arbitrary Subjects



Using URIs to Identify Resources



A Plea to Ontology Developers

• Make them publicly available!

• Define URIs as unique identifiers for the concepts in your ontologies – including the relationship types

– http://psi.fao.org/disease/#bse

• Follow the Recommendations of the OASIS Published Subjects TC:– Make sure they resolve to human-readable resources– Guarantee their stability

• This will allow human users to use different terminology– Bovine Spongiform Encephalopathy (?), BSE– Mad Cow Disease– Kugalskap, La vache folle, etc.

• And enable interoperability and reuse across applications:– Topic Maps, RDF, DAML+OIL, OWL, KIF, XML, etc.



Topic Maps for Machine Agents

• A formal data structure suitable for data processing

• Support for rich semantic queries

• High degree of built-in semantics simplifies application development

• Published Subjects enable widespread and spontaneous knowledge interchange

• International standard interchange syntax

• Potential for wide adoption means more data for agents



Topic Maps for Human Agents

• A way of representing knowledge that corresponds to how humans think about the world

– Organized around subjects not resources– Direct support for context sensitivity

• A level of built-in semantics that makes the model easy to understand– Distinguishes between names, occurrences and associations– Privileges the class-instance relationship

• Associative model matches how the brain works– Typed associations provide a rich and intuitive navigational interface



Topic Map-Driven Knowledge Portals

• Let the index drive the presentation!– The Topic Map structure governs the application – and the knowledge

• Users navigate intuitively from topic to topic– Having found the appropriate topic, they

• immediately see all recorded explicit knowledge• can dip down into information resources to “extract” implicit knowledge

• Publisher benefits:– Easier content maintenance (simply update the Topic Map)– Easier link maintenance (links are in separate layer, not in content)– New portals easy to derive from same content

• User benefits:– Shorter click-through– Easier, more intuitive navigation mirrors associative way of thinking– Far greater structural consistency means less confusion

Demo of the OperaMap portalhttp://www.ontopia.net/operamap



For More Information

• “Getting Started with Topic Maps”

• Ontopia web site– http://www.ontopia.net

• /me– [email protected]

• Finally– Ontopia is the world’s leading Topic Map company– We are interested in participating in EU projects– Please contact me for more details

An introduction to topic maps,ontologies and published subjects

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