An Overview and Underview of the Semantic Web Tim Finin recommend University of Maryland Baltimore County tell register tell Semantic Web for Science Workshop Newark NJ, October 2002 register http: //umbc. edu/~finin/talks/swsw 02/ 1
Overview n The Problem: building intelligent information systems n The Semantic web as part of the solution n Background on the semantic web n Comments and Conclusions UMBC an Honors University in Maryland 2
The problem n I’ve been engaged in research aimed at developing intelligent information systems for thirty years. n The problem is hard, progress is slow, but the incremental results are worth it. n It’s a task for many generations to come. n Today’s environment is very different than that in 1972. UMBC an Honors University in Maryland 3
They way we were… UMBC an Honors University in Maryland AN IBM 360 circa 1972 4
They way we will be… UMBC an Honors University in Maryland 5
What’s new? n Internet. Virtually of the computers in the world have been connected. n Scale. Every day many more computing and communication devices are joining. n Power. Raw computing power continues to climb. n Wireless. New technologies (GSM, 802. 11, Bluetooth, UWB? , IR, etc) are creating a pervasive, ubiquitous computing environment n Web. Anyone can publish content and provide services, powerful search engines support discovery, evolving standards enhance interoperability UMBC an Honors University in Maryland 6
The way we will be… People, agents, devices, & services need to Find others in their environment n Describe the services they offer and seek n Exchange APIs n Negotiate for services, permissions, privacy, payment, … n Reason about services to create composite services n Coordinate and cooperate as needed n Sense their context and the activities of humans n Deal with new entities never before encountered n And to do this dynamically UMBC an Honors University in Maryland 7
Semantic Web n I’ll argue that the semantic web provides a good approach, language and tools to support the development of intelligent information systems in this environment. n This isn’t obvious, since the SW seems grounded in the “traditional” hypertext on the wired web. n But, the principles which drive it are the right ones for agents as well as pervasive computing. n And, by grounding agents in web technology, they make it out of the lab. n Next: overview of Semantic Web UMBC an Honors University in Maryland 10
W 3 C’s Semantic Web Goals n Focus on machine consumption: "The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation. " -- Berners-Lee, Hendler and Lassila, The Semantic Web, Scientific American, 2001 n Whereas the Web has made people smarter, the SW will make machines smarter. n The current Web stores things whereas the SW enables agents which do things. UMBC an Honors University in Maryland 11
Origins of the Semantic Web Capsule history Tim Berners-Lee proposed WWW as a Web of relationships among named objects (89) n Guha designed MCF (~94) n XML+MCF=>RDF (~96) n RDF+OO=>RDFS (~99) n RDFS+KR=>DAML+OIL (00) n W 3 C’s SW activity (01) n W 3 C’s OWL (02? ) n UMBC an Honors University in Maryland http: //www. w 3. org/History/1989/proposal. html 12
Why is this hard? UMBC an Honors University in Maryland after Frank van Harmelen and Jim Hendler 14
What a web page looks like to a machine… And understanding natural language is easier than images! “Webscraping” is mostly done by hand crafted rules or rules generated by supervised learning Either way, the rules can break when the page structure changes. UMBC an Honors University in Maryland after Frank van Harmelen and Jim Hendler 15
OK, so HTML is not helpful Could we tell the machine what the different parts of the text represent? title speaker time location abstract biosketch host UMBC an Honors University in Maryland after Frank van Harmelen and Jim Hendler 16
XML to the rescue? <title> <speaker> <time> <location> </title> </speaker> </time> </location> <abstract> XML fans propose creating a XML tag set to use for each application. For talks, we can choose <title>, <speaker>, etc. </abstract> <biosketch> </biosketch> <host> UMBC an Honors University in Maryland </host> after Frank van Harmelen and Jim Hendler 17
XML machine accessible meaning <title> <speaker> <time> <location> <abstract> <biosketch> <host> UMBC an Honors University in Maryland </title> </speaker> </time> </location> But, to your machine, the tags still look like this…. The tag names carry no meaning. XML DTDs and Schemas have little or no </biosketch>semantics. </abstract> </host> after Frank van Harmelen and Jim Hendler 18
XML Schema helps XML Schemas provide a simple mechanism to define shared vocabularies. <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Schema file <title> <speaker> <time> <location> <abstract> <biosketch> <host> UMBC an Honors University in Maryland </title> </speaker> </time> </location> </abstract> </biosketch> </host> <title> <speaker> <time> <location> <abstract> <biosketch> <host> </title> </speaker> </time> </location> </abstract> </biosketch> </host> after Frank van Harmelen and Jim Hendler 19
But there are many schemas <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Schema file 1 <title> <speaker> <time> <location> <abstract> <biosketch> <host> UMBC an Honors University in Maryland </title> </speaker> </time> </location> </abstract> </biosketch> </host> <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Schema file 42 <title> <speaker> <time> <location> <abstract> <biosketch> <host> </title> </speaker> </time> </location> </abstract> </biosketch> </host> after Frank van Harmelen and Jim Hendler 20
There’s no way to relate schema <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Schema file 1 <title> <speaker> <time> <location> <abstract> <biosketch> <host> UMBC an Honors University in Maryland </title> </speaker> </time> </location> </abstract> </biosketch> </host> <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Schema file 42 <title> <speaker> <time> <location> <abstract> <biosketch> <host> </title> </speaker> </time> </location> </abstract> </biosketch> </host> Either manually or automatically -- XML Schema is very weak on semantics 21
Ontologies can help … n n An ontology defines the terms used to describe and represent an area of knowledge. Ontologies are used by people, databases, and applications that need to share domain information (a domain is just a specific subject area or area of knowledge, like medicine, tool manufacturing, real estate, automobile repair, financial management, etc. ). Ontologies include computer-usable definitions of basic concepts in the domain and the relationships among them. . . They encode knowledge in a domain and also knowledge that spans domains. In this way, they make that knowledge reusable. UMBC an Honors University in Maryland Working Draft, Web Ontology Working Group. 22
Ontologies can help … Catalog/ID Thesauri “narrower term” relation DB Schema UMLS Wordnet Terms/ glossary Simple Taxonomies UMBC an Honors University in Maryland Formal is-a Frames (properties) RDF OO Informal is-a RDFS Disjointness, Inverse, part of… DAML CYC OWL Formal instance IEEE SUO Value Restriction General Logical constraints Expressive Ontologies After Deborah L. Mc. Guinness (Stanford) 23
An Ontology level is needed <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" XML Ontology 512 references <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Ontology 256 imports <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Ontology 1 = <> Ontologies add • Structure • Constraints • Mappings • Sharing imports <? xml version="1. 0" encoding="utf-8"? > <xs: schema xmlns: xs="http: //www. w 3. org/2001/XMLSchema"> <xs: element name="book"> <xs: complex. Type> <xs: sequence> <xs: element name="title" type="xs: string"/> <xs: element name="author" type="xs: string"/> <xs: element name="character" min. Occurs="0" max. Occurs="unbounded"> <xs: complex. Type> <xs: sequence> <xs: element name="name" type="xs: string"/> <xs: element name="friend-of" type="xs: string" min. Occurs="0" max. Occurs="unbounded"/> <xs: element name="since" type="xs: date"/> <xs: element name="qualification" type="xs: string"/> </xs: sequence> </xs: complex. Type> </xs: element> </xs: sequence> <xs: attribute name="isbn" type="xs: string"/> </xs: complex. Type> </xs: element> </xs: schema> XML Ontology 42 We need a way to define ontologies in XML UMBC an Honors University in Maryland So we can relate them So machines can understand (to some degree) their meaning 24
Ontologies vary… n Ontologies vary greatly in their n Scope n Complexity n Level of detail n Kind of knowledge encoded n… n Two UMBC an Honors University in Maryland examples… 25
Dublin Core -- A Simple Ontology Developed by an OCLC sponsored workshop in Dublin ~95 as a standard for metadata for digital library resources on web n Consists of 15 core attributes n http: //dublincore. org/ n Neutral on how DC should be represented n HTML found to be inadequate for representing complexities of structured use of DC n Available as an RDF schema. n UMBC an Honors University in Maryland 15 DC elements Content elements n n n n Coverage Description Relation Source Subject Title Type Intellectual Property n n Contributor Creator Publisher Right Instantiation n n Date Format Identifier Language 26
Cyc – a complex ontology n Cyc is a large, general purpose ontology with associated reasoning tools developed over the past ~20 years by MCC and now Cycorp Cyc KB has > 100 k terms. n Terms are axiomatized by > 1 M handcrafted assertions n Cyc inference engine has > 500 heuristic level modules n n Goal is to encode knowledge for “common sense reasoning” needed by applications (e. g. , NLP) n Available free in limited form from http: //opencyc. org/ UMBC an Honors University in Maryland 27
Today and tomorrow n We are in a good position to use simple ontologies like DC today n This is happening (e. g. , Adobe’s XMP) n We hope to be able to make effective use ontologies like Cyc in the coming decade There are skeptics… n It’s a great research topic… n UMBC an Honors University in Maryland 28
“The Semantic Web will globalize KR, just as the WWW globalize hypertext” TBL’s semantic web vision -- Tim Berners-Lee you are here UMBC an Honors University in Maryland 29
Semantic web languages today n Today there are, IMHO, two semantic web languages n DAML+OIL – Darpa Agent Markup Language http: //www. daml. org/ n RDF – Resource Description Framework http: //www. w 3. org/RDF/ n and one under development by the W 3 C n OWL – Ontology Web Language http: //www. w 3. org/2001/sw/ n Topic maps (http: //topicmaps. org/) are another breed n with more to come…. UMBC an Honors University in Maryland 30
RDF is the first SW language Graph XML Encoding <rdf: RDF ……. . > <…. > </rdf: RDF> Good for Machine Processing RDF Data Model Good For Human Viewing Triples stmt(doc. Inst, rdf_type, Document) stmt(person. Inst, rdf_type, Person) stmt(inroom. Inst, rdf_type, In. Room) stmt(person. Inst, holding, doc. Inst) stmt(inroom. Inst, person. Inst) UMBC an Honors University in Maryland Good For Reasoning 32
Simple RDF Example dc: Title http: //umbc. edu/~finin/talks/idm 02/ “Intelligent Information Systems on the Web and in the Aether” dc: Creator bib: Aff http: //umbc. edu/ UMBC an Honors University in Maryland bib: name “Tim Finin” bib: email “finin@umbc. edu” 33
XML encoding for RDF <rdf: RDF xmlns: rdf="http: //www. w 3. org/1999/02/22 -rdf-syntax-ns#" xmlns: dc="http: //purl. org/dc/elements/1. 1/" xmlns: bib="http: //daml. umbc. edu/ontologies/bib/"> <description about="http: //umbc. edu/~finin/talks/idm 02/"> <dc: title>Intelligent Information Systems on the Web and in the Aether</dc: Title> <dc: creator> <description> <bib: Name>Tim Finin</bib: Name> <bib: Email>finin@umbc. edu</bib: Email> <bib: Aff resource="http: //umbc. edu/" /> </description>“ian@goo. org” </dc: Creator> </description> </rdf: RDF> UMBC an Honors University in Maryland 34
N triple representation n RDF can be encoded as a set of triples. n <subject> <predicate> <object>. <http: //umbc. edu/~finin/talks/idm 02/> <http: //purl. org/dc/elements/1. 1/Title> "Intelligent Information Systems on the Web and in the Aether". _: j 10949 <http: //daml. umbc. edu/ontologies/bib/Name> "Tim Finin". _: j 10949 <http: //daml. umbc. edu/ontologies/bib/Email> "finin@umbc. edu". _: j 10949 <http: //daml. umbc. edu/ontologies/bib/Aff> <http: //umbc. edu/>. _: j 10949 <http: //www. w 3. org/1999/02/22 -rdf-syntax-ns#type> <Description>. <http: //umbc. edu/~finin/talks/idm 02/> <http: //purl. org/dc/elements/1. 1/Creator> _: j 10949. <http: //umbc. edu/~finin/talks/idm 02/> <http: //www. w 3. org/1999/02/22 -rdfsyntax-ns#type> <Description>. n Note the gensym for the anonymous node (_: j 10949 ) ( UMBC an Honors University in Maryland 35
Triple Notes n RDF triples have one of two forms: n n n <URI> <URI> <quoted string> Triples are also easily mapped into logic n n <subject> <predicate> <object> <predicate>(<subject>, <object>) With type(<S>, <O>) becoming <O>(<S>) Example: n n n subclass(man, person) sex(man, male) domain(sex, animal) man(adam) age(adam, 100) ; Note: we’re not ; showing the actual ; URIs for clarity Triples are easily stored and managed in a DBMS UMBC an Honors University in Maryland 36
N 3 notation for RDF N 3 is a compact notation for triples which is easier for people to read and edit Example: @prefix log: <http: //www. w 3. org/2000/10/swap/log#>. : Person a rdfs: Class. : Woman a rdfs: Class; rdfs: sub. Class. Of : Person. : Eve a : Woman; age “ 100”. : sister a rdf: Property. : sister rdfs: domain : Person; rdfs: range : Woman. UMBC an Honors University in Maryland 37
RDF Schema (RDFS) n RDF Schema adds taxonomies for classes & properties n n and some metadata. n n sub. Class and sub. Property domain and range constraints on properties Several widely used KB tools can import and export in RDFS UMBC an Honors University in Maryland Stanford Protégé KB editor • Java, open sourced • extensible, lots of plug-ins • provides reasoning & server capabilities 38
RDFS supports simple inferences 100% Better than XML!! RDF ontology plus some RDF statements may imply additional RDF statements. n This is not true of XML. n Example: instance ontology n An New and Improved! domain(parent, person) range(parent, person) subproperty(mother, parent) range(mother, woman) mother(eve, cain) Implies: subclass(woman, person) parent(eve, cain) person(eve) person(cain) woman(eve) n This is part of the data model and not of the accessing/processing code UMBC an Honors University in Maryland 39
RDF is being already in use n RDF has a solid specification n n RDF is being used in a number of W 3 C specifications n n n CC/PP (Composite Capabilities/Preference Profiles) http: //www. w 3. org/Mobile/CCPP/ P 3 P (Platform for Privacy Preferences Project) http: //www. w 3. org/P 3 P/ And in other web standards n n n See the RDF model theory spec - http: //www. w 3. org/TR/rdf-mt/ RSS 1. 0 (RDF Site Summary) RDF calendar (~ i. Calendar in RDF) And in other systems n n n Netscape’s Mozilla web browser Open directory (http: //dmoz. org/) Adobe products via XMP (e. Xtensible Metadata Platform) UMBC an Honors University in Maryland 40
RDF is not enough, but is a good foundation n RDF lacks expressive adequacy for many tasks Only range/domain constraints (on properties) n No properties of properties (transitive, inverse etc. ) n No equivalence, disjointness, coverings, etc. n No necessary and sufficient conditions n No rules, axioms, logical constraints n n DAML+OIL extends RDF Layering makes partial knowledge available to applications which only understand RDF n NB: Building on RDF has some DAML+OIL disadvantages RDF n UMBC an Honors University in Maryland XML 41
We’re going down a familiar road KR trends 55 -65: arbitrary data structures n 65 -75: semantic networks n 75 -85: simple frame systems n 85 -95: description logics n n 95 -? ? : logic? , rules? UMBC an Honors University in Maryland Web trends 95 -97: XML as arbitrary structures n 97 -98: RDF n 98 -99: RDFS (schema) as a frame-like system n 00 -01: DAML+OIL n 02 -? ? : OWL, …? ? . . . n Only much faster! 42
DAML+OIL as a Semantic Web Language n. DAML = Darpa Agent Markup Language n DARPA program with 17 projects & an integrator developing language spec, tools, applications for SW. n. OIL = Ontology Inference Layer n An EU effort aimed at developing a layered approach to representing knowledge on the web. n. Process n Joint Committee: US DAML and EU Semantic Web Technologies participants DAML+OIL n DAML+OIL specs released 01/01 & 03/01 n See http: //www. daml. org/ n Includes model theoretic and axiomatic semantics UMBC an Honors University in Maryland 43
A Simple DAML Example <rdfs: Class about="#Animal"/> <rdfs: Class about="#Plant"> <daml: disjoint. From resource="#Animal"/> </rdfs: Class> the mixture of RDF (plant & animal are classes) and DAML (plant & animal are disjoint) n Note n If your cell phone only does RDF, it still understands some of this… UMBC an Honors University in Maryland 44
DAML+OIL RDF n DAML+OIL ontology is a set of RDF statements DAML+OIL defines semantics for certain statements n Does NOT restrict what can be said n Ontology can include arbitrary RDF n But no semantics for non-DAML+OIL statements n Adds n cardinality constraints, defined classes (=> classification), equivalence, local restrictions, disjoint classes, etc. n More n capabilities common to description logics: support for ontologies Ontology imports ontology n But not (yet) variables, quantification, and general rules UMBC an Honors University in Maryland 45
DAML in One Slide DAML is built on top of XML and RDF It allows the definition, sharing, composition and use of ontologies DAML is ~= a frame based knowledge representation language It can be used to add metadata about anything which has a URIs are a W 3 C standard generalizing URLs everything has URI UMBC an Honors University in Maryland <rdf: RDF xmlns: rdf ="http: //w 3. org/22 -rdf-syntax-ns#" xmlns: rdfs="http: //w 3. org/rdf-schema#" xmlns: daml="http: //daml. org/daml+oil#“> <daml: Ontology rdf: about=""> <daml: imports rdf: resource="http: //daml. org/daml+oil"/> </daml: Ontology> <rdfs: Class rdf: ID="Person"> <rdfs: sub. Class. Of rdf: resource="#Animal"/> <rdfs: sub. Class. Of> <daml: Restriction> <daml: on. Property rdf: resource="#has. Parent"/> <daml: to. Class rdf: resource="#Person"/> </daml: Restriction> </rdfs: sub. Class. Of> <daml: Restriction daml: cardinality="1"> <daml: on. Property rdf: resource="#has. Father"/> </daml: Restriction> </rdfs: sub. Class. Of> </rdfs: Class> <Person rdf: about=“http: //umbc. edu/~finin/"> <rdfs: comment>Finin is a person. </rdfs: comment> </Person> 46
DAML-S n DAML-S is an ontology for describing properties and capabilities of web services n Desiderata: n Ease of expressiveness n Enables automation of service use by agents n Enables reasoning about service properties and capabilities n Also appropriate for describing services in a mobile/pervasive computing environment n See http: //daml. org/services/ UMBC an Honors University in Maryland 47
W 3 C Web Ontology Working Group The WOWG is working on a recommendation for the "Web Ontology Language": OWL n 56 Members from 30 W 3 C Organizations n n n Companies: Agfa, Daimler-Chrysler, EDS, Fujitsu, Hewlett-Packard, IBM, Intel, IVIS, Lucent, Network Inference, Nisus, Nokia, Philips, Stilo, Sun, Unisys Public Sector: DISA, Electricite de France, Intelink, INTAP, MITRE, NIST Research projects/Labs: DFKI, FZI, Ibrow group, Stanford, U. Bristol, U. Maryland, U. Southhampton Invited Experts: Medical, Digital Library, Defense, Technical Co. Chairs: Jim Hendler, University of Maryland/MIND; Guus Schreiber, Univ of Amsterdam/Ibrow n http: //www. w 3. org/2001/sw/Web. Ont/ n UMBC an Honors University in Maryland 50
OWL status and publications n OWL is roughly equivalent to DAML with some renaming of properties n Current plan is to have three compliance levels: OWL lite, OWL plus n Web. Ont has published Requirements for a Web Ontology Language n Feature Synopsis for OWL Lite and OWL n OWL Web Ontology Language 1. 0 Reference n OWL Web Ontology Language 1. 0 Abstract Syntax n (forthcoming) OWL Guide n UMBC an Honors University in Maryland 52
KR meets the Web n One way to think about the semantic web is that we are creating a knowledge representation language for the Web. n This is more than just selecting an appropriate KR language and selecting an XML encoding. n The Web as an information system has many significant properties. n n n n Highly distributed Subject to disconnections and other failures Many content providers Partial and inconsistent information Not all info and services can be trusted Dynamic Evolving UMBC an Honors University in Maryland 54
SW is work in progress n There are important language aspects which need more work: rules, queries, etc. n Many tools need to be created, e. g. , Protégé plug-in for DAML+OIL n Annotation tools n n Applications need to be explored n The W 3 C is developing a new SW language n OWL: Ontology Web Language n SW ideas will migrate into other standards (e. g. , basic XML, WSDL, . NET) UMBC an Honors University in Maryland 56
Lots of Open Issues How expressive should the KR language be? n What kind of KR/reasoning system n n n On Web Ontologies n n ? One (e. g. CYC) or many (DAML) If many, composable (IEEE IFF) or monolithic (IEEE SUMO) Will general “upper ontologies” (e. g. , IEEE SUO) be useful? Will industry buy in? n n F. O. logic, fuzzy, … Or continue to explore ad hoc XML based solutions How will it be used? n As markup? As alternative content? Just both machines and people? => Only experimentation will yield answers. UMBC an Honors University in Maryland 58
Conclusions and final thoughts n SW might be a chance for us to get some AI out of the lab n Solving the symbol grounding problem n Rethinking agent communication n How do we get there UMBC an Honors University in Maryland 59
How do we get there from here? n This semantic web emphasizes ontologies – their development, use, mediation, evolution, etc. n It will take some time to really deliver on the agent paradigm, either on the Internet or in a pervasive computing environment. n The development of complex systems is basically an evolutionary process. n Random search carried out by tens of thousands of researchers, developers and graduate students. UMBC an Honors University in Maryland 64
So, we should … Start with the simple and move toward the complex E. g. , from vocabularies to FOL theories n Develop new capabilities E. g. , rules, trust, negotiation, automatic markup, … n Allow many ontologies to bloom Let natural evolutionary processes select consensus ontologies. n Support diversity in ontologies Monocultures are unstable, there should be no “The ontology for X”. n The evolution of powerful, machine readable ontologies will take many years, maybe generations But incremental benefits will easily justify the effort n UMBC an Honors University in Maryland 67
For more information n RDF http: //www. w 3. org/RDF/ n DAML+OIL http: //www. daml. org/ n OWL & W 3 C’s semantic web activity http: //www. w 3. org/2001/sw/ n Semantic web links http: //semanticweb. org/ n Next Semantic Web Conference http: //iswc. semanticweb. org/ n October 2003, Sanibel Island, SC. n UMBC an Honors University in Maryland 68
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