Ontology History of the Semantic Web l l

Ontology

History of the Semantic Web l l Web was “invented” by Tim Berners-Lee (amongst others), a physicist working at CERN TBL’s original vision of the Web was much more ambitious than the reality of the existing (syntactic) Web: “. . . a goal of the Web was that, if the interaction between person and hypertext could be so intuitive that the machine-readable information space gave an accurate representation of the state of people's thoughts, interactions, and work patterns, then machine analysis could become a very powerful management tool, seeing patterns in our work and facilitating our working together through the typical problems which beset the management l TBL (and others) have since been working towards realising this of large organizations. ” vision, which has become known as the Semantic Web l E. g. , article in May 2001 issue of Scientific American…

Scientific American, May 2001: l l Realising the complete “vision” is too hard for now (probably) But we can make a start by adding semantic annotation to web resources

Where we are Today: the Syntactic Web

The Syntactic Web is… A hypermedia, a digital library l A library of documents called (web pages) interconnected by a hypermedia of links l A database, an application platform l A common portal to applications accessible through web pages, and presenting their results as web pages l A platform for multimedia l BBC Radio 4 anywhere in the world! Terminator 3 trailers! l A naming scheme l Unique identity for those documents A place where computers do the presentation (easy) and people do the linking and interpreting (hard). l Why not get computers to do more of the hard work?

Impossible (? ) using the Syntactic Web… l l Complex queries involving background knowledge l Find information about “animals that use sonar but are not either bats or dolphins” Locating information in data repositories l Travel enquiries l Prices of goods and services l Results of human genome experiments Finding and using “web services” l Visualize surface interactions between two proteins Delegating complex tasks to web “agents” l Book me a holiday next weekend somewhere warm, not too far away, and where they speak French or English

What is the Problem? l Consider a typical web page: l Markup consists of: l rendering information (e. g. , font size and colour) l Hyper-links to related content l Semantic content is accessible to humans but not (easily) to computers…

What information can we see… WWW 2002 The eleventh international world wide web conference Sheraton waikiki hotel Honolulu, hawaii, USA 7 -11 may 2002 1 location 5 days learn interact Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire Register now On the 7 th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event … Speakers confirmed Tim berners-lee Tim is the well known inventor of the Web, … Ian Foster Ian is the pioneer of the Grid, the next generation internet …

What information can a machine see… WWW 2002 The eleventh international world wide web conference Sheraton waikiki hotel Honolulu, hawaii, USA 7 -11 may 2002 1 location 5 days learn interact Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire Register now On the 7 th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event … Speakers confirmed Tim berners-lee Tim is the well known inventor of the Web, … Ian Foster Ian is the pioneer of the Grid, the next generation internet …

Solution: XML markup with “meaningful” tags? <name>WWW 2002 The eleventh international world wide webcon </name> <location>Sheraton Honolulu, waikiki hotel hawaii, USA </location> <date>7 -11 may 2002</date> <slogan>1 location 5 days learn interact </slogan> <participants>Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire</participants> <introduction>Register now On the May Honolulu will provide the backdrop the eleventh international world wide web conference. This prestigious event … Speakers confirmed </introduction> 7 th <speaker>Tim berners-lee </speaker> <bio>Tim is the well known inventor of the Web, </bio>… of

Need to Add “Semantics” l External agreement on meaning of annotations l E. g. , Dublin Core l l Problems with this approach l l l Agree on the meaning of a set of annotation tags Inflexible Limited number of things can be expressed Use Ontologies to specify meaning of annotations l Ontologies provide a vocabulary of terms l New terms can be formed by combining existing ones l Meaning (semantics) of such terms is formally specified l Can also specify relationships between terms in multiple ontologies

Ontology: Origins and History Ontology in Philosophy a philosophical discipline—a branch of philosophy that deals with the nature and the organisation of reality l Science of Being (Aristotle, Metaphysics, IV, 1) l Tries to answer the questions: What characterizes being? Eventually, what is being?

Ontology in Linguistics Concept Relates to activates Form “Tank“ Stands for Referent ?

Ontology in Computer Science l An ontology is an engineering artifact: l l l It is constituted by a specific vocabulary used to describe a certain reality, plus a set of explicit assumptions regarding the intended meaning of the vocabulary. Thus, an ontology describes a formal specification of a certain domain: l l Shared understanding of a domain of interest Formal and machine manipulable model of a domain of interest “An explicit specification of a conceptualisation” [Gruber 93]

Definitions of Ontologies “An ontology is a formal, explicit specification of a shared conceptualization” Machine-readable Consensual Knowledge Concepts, properties relations, functions, constraints, axioms, are explicitly defined Abstract model and simplified view of some phenomenon in the world that we want to represent

Ontology l Key components l l Class Property Individuals Axiom

Class l What is a Class? l l e. g. , person, pet, old a collection of individuals (object, things, . . . ) a way of describing part of the world an object in the world (OWL Full)

Example Classes Class(pp: animal partial restriction(pp: eats some. Values. From(owl: Thing))) Class(pp: person partial pp: animal) Class(pp: man complete intersection. Of(pp: person pp: male pp: adult)) Class(pp: animal+lover complete intersection. Of(pp: person restriction(pp: has_pet min. Cardinality(3))))

Example Class(pp: vegetarian complete intersection. Of(pp: animal restriction(pp: eats all. Values. From(complement. Of(pp: animal))) restriction(pp: eats all. Values. From( complement. Of(restriction(pp: part_of some. Values. From(pp: animal))))))) Disjoint. Classes(pp: young pp: adult)

Properties l What is a Property? l l e. g. , has father, has pet, service number a collection of relationships between individuals (and data) a way of describing a kind of relationship between individuals an object in the world (OWL Full)

Example Properties Object. Property(pp: eaten_by) Object. Property(pp: eats inverse. Of(pp: eaten_by) domain(pp: animal)) Object. Property(pp: has_pet domain(pp: person) range(pp: animal)) Object. Property(pp: is_pet_of inverse. Of(pp: has_pet)) Data. Property(pp: service_number range(xsd: integer)) Sub. Property. Of(pp: has_pet pp: likes)

Individuals l l l objects in the world belong to classes (members of the class) are related to other objects and to data values via properties

Example Individuals Individual(pp: Tom type(owl: Thing)) Individual(pp: Dewey type(pp: duck)) Individual(pp: Rex type(pp: dog) value(pp: is_pet_of pp: Mick)) Individual(pp: Mick type(pp: male) value(pp: reads pp: Daily+Mirror) value(pp: drives pp: Q 123+ABC)) Individual(pp: The 42 type(pp: bus) value(pp: service_number "42“^^xsd: integer))

Axiom l l An axiom is a sentence that is assumed to be true without proof. Example l l l If any two animals are siblings, then there exists someone who is the mother of both of them. with the axiom: (=> (sibling ? sib 1 ? sib 2) (exists (? mom) (and (hasmother ? sib 1 ? mom) (has-mother ? sib 2 ? mom)))

Example of a Taxonomy Flight Subclass-of American Airlines Flight Iberia Flight Subclass-of British Airways Flight Subclass-of AA 7462 Disjoint-Decomposition Subclass-of AA 2010 AA 0488 IB 6274 BA 0068 BA 0066 BA 0069

An example: Knowledge Web Ontologies has associated event / ha s as has asso soci ated ciate has / is associated with d/i s ass ocia ted is author of / has author Person Ontology is c has ontac bel con t pe ong tac rson s to t pe / is rso / for n me db y has contact person Organization Ontology Documentation Ontology r. A. Q tne s r a a r h tne p by t g n d r n a e i t p pa hor tici enera t r u a a p is g ad has / e l s ate has r e gen is associated with r in Event Ontology has associated / leads is involved in / has p leader works in / has p p has person leader is de live in r de ks by ea or r l / w ped lo cto ner ra ve nt part de co is as ved n / / h ol s i ds inv ate lea as ticip h r pa is WP leader / has person leader Project Ontology

Example: Event Ontology Event International Conference Review International Workshop EPMB Meeting Management Project Meeting KW Area Meeting KW Plennary Meeting Research Area Meeting Education Area Meeting PMB Meeting Industry Area Meeting

Example: Documentation Ontology Documentation Additional Documentation Management Documentation Technical Documentation Publication Templates Manual Article Slides Thesis Master Thesis Deliverable Book . . . Agenda Cost Statement EC Templates Fax Mail Minutes. . . Periodic Report Project Proposal . . . Ph. D Thesis

Example: Relationships between Person, Project and Documentation has associated WP workload Milestone has participant with workload Workpackage is made up of is deliver in has Project Ontology Task leads works in Documentation Ontology is involved in Person Ontology is WP leader Person is author of has contact person Deliverable