The Semantic Web

Deborah McGuinness

Associate Director and Senior Research Scientist

Knowledge Systems Laboratory

Stanford University

Stanford, CA USA

dlm@ksl.stanford.edu

http://www.ksl.stanford.edu/people/dlm

Today: Rich Information Source for Human Manipulation/Interpretation

Human

Human

“I know what was input”

• Global documents and terms indexed and available for search• Search engine interfaces• Entire documents retrieved according to relevance (instead of

answers)• Human input, review, assimilation, integration, action, etc.• Special purpose interfaces required for user friendly applications

The web knows what was input but does little interpretation, manipulation, integration, and action

Information Discovery… but not much more

• Human intensive (requiring input reformulation and interpretation)

• Display intensive (requiring filtering)• Not interoperable• Not agent-operational• Not adaptive• Limited context• Limited service

Analogous to a new assistant who is thorough yet lacks common sense, context, and adaptability

Future: Rich Information Source for Agent Manipulation/Interpretation

Human

Agent

Agent

“I know what was meant”

• Understand term meaning and user background• Interoperable (can translate between applications)• Programmable (thus agent operational)• Explainable (thus maintains context and can adapt)• Capable of filtering (thus limiting display and

human intervention requirements)• Capable of executing services

Semantic Markup

Languages such as DAML+OIL(www.daml.org)• Encoding background info• User modeling info• Annotating web pages• Annotating services thereby limiting needs for human disambiguation input, human

interpretation, multiple answer display, translation assistance, agent assistance, adaptivity support, etc.)

Ontologies

DAML-enabled web pages

The Semantic Web enables…

• New models of intelligent services

• E-commerce solutions

• M-commerce

• Web assistants

• …

•E-commerce solutions

•M-commerce

The Semantic Web Enables…

New forms of web assistants/agents that act on a human’s behalf requiring less from humansand their communication devices…

Under the coversMeaning needs to be encoded, understood, and

reasoned with.

-- Ontologies capture meanings of terms and their interrelationships

What is an Ontology?

Catalog/ID

GeneralLogical

constraints

Terms/glossary

Thesauri“narrower

term”relation

Formalis-a

Frames(properties)

Informalis-a

Formalinstance

Value Restrs.

Disjointness, Inverse, part-

of…

Ontologies and importance to E-Commerce

Simple ontologies (taxonomies) provide:• Controlled shared vocabulary (search engines, authors,

users, databases, programs/agents all speak same language)• Site Organization and Navigation Support• Expectation setting (left side of many web pages)• “Umbrella” Upper Level Structures (for extension)• Browsing support (tagged structures such as Yahoo!)• Search support (query expansion approaches such as

FindUR, e-Cyc)• Sense disambiguation

Ontologies and importance to E-Commerce II

• Consistency Checking• Completion• Interoperability Support• Support for validation and verification testing (e.g.

http://ksl.stanford.edu/projects/DAML/chimaera-jtp-cardinality-test1.daml )

• Configuration support• Structured, “surgical” comparative customized

search• Generalization/ Specialization• … Foundation for expansion and leverage

A Few Observations about Ontologies– Simple ontologies can be built by non-experts

• Verity’s Topic Editor, Collaborative Topic Builder, GFP, Chimaera, Protégé, OIL-ED, etc.– Ontologies can be semi-automatically generated

• from crawls of site such as yahoo!, amazon, excite, etc.• Semi-structured sites can provide starting points

– Ontologies are exploding (business pull instead of technology push)• most e-commerce sites are using them - MySimon, Amazon, Yahoo! Shopping, VerticalNet,

etc.• Controlled vocabularies (for the web) abound - SIC codes, UMLS, UN/SPSC, Open

Directory (DMOZ), Rosetta Net, SUO • Business interest expanding – ontology directors, business ontologies are becoming more

complicated (roles, value restrictions, …), VC firms interested,• DTDs are making more ontology information available • Markup Languages growing XML, RDF, DAML, RuleML, xxML• “Real” ontologies are becoming more central to applications

Implications and Needs

• Ontology Language Syntax and Semantics (DAML+OIL)

• Environments for Creation and Maintenance of Ontologies

• Training (Conceptual Modeling, reasoning implications, …)

Issues– Collaboration among distributed teams– Interconnectivity with many systems/standards– Analysis and diagnosis– Scale– Versioning– Security– Ease of use– Diverse training levels /user support– Presentation style– Lifecycle– Extensibility

Chimaera – A Ontology Environment Tool

An interactive web-based tool aimed at supporting:•Ontology analysis (correctness, completeness, style, …)•Merging of ontological terms from varied sources•Maintaining ontologies over time•Validation of input

• Features: multiple I/O languages, loading and merging into multiple namespaces, collaborative distributed environment support, integrated browsing/editing environment, extensible diagnostic rule language

• Used in commercial and academic environments

• Available as a hosted service from www-ksl-svc.stanford.edu

• Information: www.ksl.stanford.edu/software/chimaera

XML• World Wide Web Consortium (W3C)

standard• Provides important solution to syntax

problem and simple semantics and schemas:

<SSN>444-23-2656</SSN>

• Now we can describe the meaning of words• Many applications of XML appearing:

– Geographic Markup Language (GML)– Extensible rights Markup Language (XrML)– Chemical Markup Language (CML)

Problem: Limited semantics and ontology

DARPA Agent Markup Language

• Builds on top of XML and RDF• Provides rich ontology

representation• Key starting point for W3C

Semantic Web activity• Future releases will provide logic

and rules capabilities

Problem: Tools to help create DAML ontologies, markup, and to facilitate access are still emerging

EXAMPLES

<html> <head> <TITLE>Fred Jones</TITLE> </head><body> <H1>Information About Fred Jones</H1><P>Fred Jones is in the U.S. Air Force. He is a Captain stationed at AFRL. </P> </body> </html>

HTML

<person><name>Fred Jones</name><employer>U.S. Air Force</employer><station>AFRL</station><rank>Captain</rank></person>

XML<rdf:RDF  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"  xmlns:daml="http://www.daml.org/2001/03/daml+oil#" xmlns:dod="http://www.dod.mil/personnel#"  xmlns:af="http://www.af.mil/personnel#"  xmlns:afrl="http://www.rl.af.mil/personnel#"  <dod:Officer rdf:ID="fsmith">    <dod:givenName>Fred</dod:givenName>    <dod:surname>Smith</dod:surname>    <dod:service rdf:resource="http://www.dod.mil/services#AirForce"/>  <af:rank rdf:resource="http://www.af.mil/personnel#Captain"/>    <af:station rdf:resource="http://www.af.mil/stations#AFRL_Rome"/>   

<daml:equivalentTo rdf:resource="ssn:123-45-6789"/>    </dod:Officer></rdf:RDF>

DAML

DAML Status

• DAML ontology language specification released and in use

• DAML services language specification draft released

• http://www.daml.org provides public Web site with DAML information

• Research and corporate teams are developing DAML tools

• Supported by W3C in the Semantic Web Activity

• Endorsed by companies and interest growing

TrustworthyWeb

Resources

HyperText Markup LanguageHyperText Transfer Protocol

Resource Description FrameworkeXtensible Markup Language Self-Describing Documents

Foundation of the Current Web

Proof, Logic andOntology Languages Shared terms/terminology

Machine-Machine communication

1990

2000

2010?

(from Berners-Lee, Hendler; Nature, 4/01)

Discussion/Conclusion• Ontologies are exploding; core of many applicationsOntologies are exploding; core of many applications• Business “pull” is driving ontology language tools and languagesBusiness “pull” is driving ontology language tools and languages• New generation applications need more expressive ontologies New generation applications need more expressive ontologies

and more back end reasoningand more back end reasoning• New generation users (the general public) need more support New generation users (the general public) need more support

than previous users of KR&R systemsthan previous users of KR&R systems• Scale and distribution of the web force mind shiftScale and distribution of the web force mind shift

• Markup languages will revolutionize web applicationsMarkup languages will revolutionize web applications• Agents can be human proxies enabling new applications and Agents can be human proxies enabling new applications and

modes of interactionmodes of interaction

Some Pointers

• Ontologies Come of Age Paper: http://www.ksl.stanford.edu/people/dlm/papers/ontologies-come-of-age-abstract.html

• Ontologies and Online Commerce Paper: http://www.ksl.stanford.edu/people/dlm/papers/ontologies-and-online-commerce-abstract.html

• DAML+OIL: http://www.daml.org/

Extras

What Is An Agent?

• Software module• Intended to act as a proxy for you

in some way• May be:

– Tightly controlled – Autonomous– Mobile

Why Is This Important?

• Humans work sequentially• Agents work in parallel and 24x7• Therefore, agents can be a major

productivity multiplier

Web Trends• Web is evolving from a provider of documents and images (information retrieval)

• To a provider of services• Web service discovery -Find me an airline service that offers flights to Singapore • Web service execution -Buy me “Harry Potter and the Sorcerer’s Stone” at

www.amazon.com

• Web service selection, composition and interoperation -Make my travel arrangements for my Internet World conference trip

• Both retrieval and services lend themselves to agent technologies

Problems

• Average Web searches examine only 25% of available information

• Web searches return a lot of unwanted information

• Information content of the Web doubles approximately every six months

• Problem continues to worsen as Web grows