The Semantic Web
(Current State and
Directions)
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
McGuinness
NSF/NCAR October 30, 2002
Outline
• Web: today and tomorrow
– The key to tomorrow’s web is semantics
• Semantics on the web requires:
– Language for encoding meaning (XML, RDF/S ->
DAML+OIL, OWL)
– Ontologies (Term descriptions and their
interrelationships)
– Tools
• Conclusion and Pointers
McGuinness
NSF/NCAR October 30, 2002
Today: Rich Information Source for
Human Manipulation/Interpretation
Human
Human
Human
McGuinness
NSF/NCAR October 30, 2002
Human
“I know what was input”
The web knows what text was input (and is great
at information dissemination) but does little
interpretation, manipulation, integration, and
action.
Analogous to a new assistant who is thorough yet
lacks common sense, context, adaptability, and
the ability to interpret for you
McGuinness
NSF/NCAR October 30, 2002
Tomorrow: Rich Information Source for
Agent Manipulation/Interpretation
Human
Agent
Agent
McGuinness
NSF/NCAR October 30, 2002
“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
McGuinness
NSF/NCAR October 30, 2002
Layer Cake Foundation
McGuinness
NSF/NCAR October 30, 2002
Semantic Markup
In languages such as OWL, DAML+OIL
(http://www.w3.org/2001/sw/WebOnt/,
http://www.daml.org), we capture
• Background info
• User modeling info
for
• Annotating web pages (man/automatically)
• Annotating services
Ontologies
DAML/OWLenabled web
pages
thereby limiting needs for human disambiguation input, human
interpretation, multiple answer display, translation assistance,
agent assistance, adaptivity support, etc.)
McGuinness
NSF/NCAR October 30, 2002
DAML/OWL Language
•Extends vocabulary of
XML and RDF/S
•Rich ontology
representation language
•Language features
chosen for efficient
implementations
Frame Systems
Web Languages
RDF/S
XML
DAML-ONT
DAML+OIL
OWL
OIL
Formal Foundations
Description Logics
FACT, CLASSIC, DLP, …
McGuinness
NSF/NCAR October 30, 2002
W3C WEBONT catches on….
• Includes over 50 members from over 30 international organizations.
– Industry including:
• Large companies such as Daimler Chrysler, EDS, Fujitsu, HP, IBM, Intel,
Lucent, Motorola, Nokia, Philips Electronics, Sun, Unisys, …
• Newer/smaller companies such as IVIS Group, Network Inference, Stilo
Technology, Unicorn Solutions, …
– Government and Not-For-Profits:
• Defense Information Systems Agency, Interoperability Technology
Association for Information Processing, Japan (INTAP) , Intelink Mgt Office,
Mitre,
• ARDA, CIA, DARPA, DIA, NCI, NIH, NIST, NSF, …
– Universities and Research Centers:
• Stanford University, University of Bristol, University of Maryland, University
of Southamptom, …
• DFKI (German Research Center for Artificial Intelligence),
Forschungszentrum Informatik
– Invited Experts
• Well-known academics from non-W3C members
McGuinness
NSF/NCAR October 30, 2002
OWL Lite Features
•
•
•
•
•
•
RDF Schema Features
– Class, rdfs:subClassOf , Individual
– rdf:Property, rdfs:subPropertyOf
– rdfs:domain , rdfs:range
Equality and Inequality
– sameClassAs , samePropertyAs , sameIndividualAs
– differentIndividualFrom
Restricted Cardinality
– minCardinality, maxCardinality (restricted to 0 or 1)
– cardinality (restricted to 0 or 1)
Property Characteristics
– inverseOf , TransitiveProperty , SymmetricProperty
– FunctionalProperty(unique) , InverseFunctionalProperty
– allValuesFrom, someValuesFrom (universal and existential local range
restrictions)
Datatypes
– Following the decisions of RDF Core.
Header Information
– imports , Dublin Core Metadata , versionInfo
McGuinness
NSF/NCAR October 30, 2002
OWL Features
•
Class Axioms
–
–
–
–
•
oneOf (enumerated classes)
disjointWith
sameClassAs applied to class expressions
rdfs:subClassOf applied to class expressions
Boolean Combinations of Class Expressions
– unionOf
– intersectionOf
– complementOf
•
Arbitrary Cardinality
– minCardinality
– maxCardinality
– cardinality
•
Filler Information
– hasValue Descriptions can include specific value information
McGuinness
NSF/NCAR October 30, 2002
OWL Lite and OWL
• Feature Synopsis:
http://www.w3.org/TR/owl-features/
• Guide:
http://www.w3.org/TR/owl-features/
• Reference Description:
http://www.w3.org/TR/owl-ref/
• Abstract Syntax:
http://www.w3.org/TR/owl-absyn/
McGuinness
NSF/NCAR October 30, 2002
Do I have to build the ontologies
myself? Maybe not….Ontologies
(suitable for reuse) are exploding
• Upper Level Ontologies
– UNSPSC, SUO, OpenCyc, OpenDirectory, TAP, …
• Specialized Ontologies
– UMLS, SNOMED, GO, CIA World Fact book, DAML-S…, even
vc’s – Vulcan,…
• Ontology Libraries
– http://www.daml.org/ontologies/
– http://www.ksl.stanford.edu/ontolingua
• “Advisory” bodies
– Semantic Web Science Foundation, NIST, Ontology.org, …
McGuinness
NSF/NCAR October 30, 2002
Ontologies in most areas …
including the environment
Quick web search yielded:
• Semantic Web for Earth and Environmental Terminology –JPL.
http://oceanesip.jpl.nasa.gov/sweet
• National Institute for environmental eScience – Cambridge http://www.niees.ac.uk/
• Gene Ontology – “dynamic controlled vocabulary that can be applied
to all organisms” http://www.geneontology.org/
• Design and Creation of Ontologies for Environmental Information
Retrieval- Telecordia - http://sern.ucalgary.ca/KSI/KAW/KAW99/papers/Kashyap1/kashyap.pdf
• Ontologies of environmental applications for a digital library of
scientific collections - http://dlforum.external.forth.gr:8080/papers/EnviroInfo.pdf
• Waste water ontology – decision support for wastewater treatment
processes - http://citeseer.nj.nec.com/ceccaroni00wawo.html
•
... Many others …
McGuinness
NSF/NCAR October 30, 2002
Tools
Tools developing: http://www.daml.org/tools/
Annotation
Browser
Crawler
Editor
Graph Visualizer
Transformation
Validator
Importer
Inference Engine
Ontology Translation
Persistence
Query Tools
RDMS Mapping
Report Generation
Search
Ontology Analyzer
Ontology Editor
Merging
Many are in research labs, but companies emerging and lasting…
Network Inference, Sandpiper, Ontoprise, AppliedSemantics, Sentius, ….
McGuinness
NSF/NCAR October 30, 2002
Conclusion/Discussion
• The Semantic Web is in its infancy today but is ready for
applications
• Markup languages, ontologies, and some tools are ready
for use
• Specialized tools are buildable/usable today
• Semantic web can be leveraged to support: (items from
Tim, Margaret, Dan, David’s presentations):
interoperability, modeling, synthesis, integrity checking, prediction,
information dissemination, quick start to “poor man’s
managed/curated data repositories”, foundation for “richer man’s
repository, foundation for new communication mode, distributed
collaboration, knowledge mgmt, knowledge from data,
“democratizing information”, “build between”, …
• Input welcome: if you need something from the semantic
web community you don’t see, tell us
McGuinness
NSF/NCAR October 30, 2002
Some Pointers
• Ontologies Come of Age Paper:
http://www.ksl.stanford.edu/people/dlm/papers/
ontologies-come-of-age-abstract.html
• OWL: http://www.w3.org/TR/owl-features/,
http://www.w3.org/TR/owl-ref/
• DAML+OIL: http://www.daml.org/ ,
http://www.w3.org/TR/daml+oil-reference
McGuinness
NSF/NCAR October 30, 2002
Extras
McGuinness
NSF/NCAR October 30, 2002
What is an Ontology?
Catalog/
ID
Thesauri
“narrower
term”
relation
Terms/
glossary
McGuinness
Frames General
Formal
is-a (properties) Logical
constraints
Informal
is-a
Formal
instance
NSF/NCAR October 30, 2002
Disjointness,
Value Inverse, partRestrs. of…
Stated goals of Semantic Web
• Define conventions for applications that exchange
metadata on the Web
• Enable vocabulary semantics to be defined by communities
of expertise, not W3C or other standards bodies
• Provide for the fine-grained mixing of diverse metadata
• Making it cost-effective for people to effectively record
their knowledge.
• Ultimate goal - the design of enabling technologies to
support machine facilitated global knowledge exchange
McGuinness
NSF/NCAR October 30, 2002
DARPA DAML Program
• Began in August 2000 Kickoff meeting
• 19 Research groups supported
• Initial ontology language aims to extend
XML, RDF/S, benefit from frames, benefit
from principled KR systems like
Description Logics
• DAML-ONT released in Oct. 2000
• DAML+OIL released in March 2001
McGuinness
NSF/NCAR October 30, 2002
DAML+OIL -> W3C
• W3C Webont working group formed with
DAML+OIL submission as starting point
http://www.w3.org/Submission/2001/12/
• Web Ontology Working Group in the W3C
Semantic Web Activity aimed at “extending
the semantic reach of current XML and
RDF meta-data efforts. “
McGuinness
NSF/NCAR October 30, 2002
WEBONT cont.
• Quarterly Face to Face meetings in
–
–
–
–
Murray Hill: http://www.w3.org/2001/sw/WebOnt/ftf1.html
Amsterdam: http://www.w3.org/2001/sw/WebOnt/ftf2.html
Stanford: http://www.w3.org/2001/sw/WebOnt/ftf3.html
Bristol: http://www.w3.org/2001/sw/WebOnt/ftf4
– Expected recommendation status at w3c meeting in march.
• Interesting Documents:
– DAML+OIL submission – full spec with reference description,
walkthrough, FOL and model theoretic semantics,
http://www.w3.org/TR/daml+oil-reference
– Use Case and requirements document:
http://www.w3.org/TR/webont-req/
McGuinness
NSF/NCAR October 30, 2002
Contact Information
dlm@ksl.stanford.edu
www.ksl.stanford.edu/people/dlm
McGuinness
NSF/NCAR October 30, 2002
Some Observations…
• Markup Languages are growing in
acceptance and expressive power
• User base, tool base, ontology base growing
• Ontology-enhanced applications springing
up (not just in ivory towers like FindUR,
eCyc, …)
McGuinness
NSF/NCAR October 30, 2002
Simple Ontology-Enhanced Apps
McGuinness
NSF/NCAR October 30, 2002
McGuinness
NSF/NCAR October 30, 2002