Semantic Web for the Working Ontologist Dean Allemang Jim Hendler SNU IDB laboratory

Semantic Web for the Working OntologistDean Allemang, Jim Hendler Working Ontology Contents 2 ■ Chapter 1 What is the Semantic Web? ■ Chapter 2 Semantic Modeling ■ Chapter 3 RDF-The Basis of the semantic Web ■ Chapter 4 Semantic Web Application Architecture ■ Chapter 5 RDF and Inferencing ■ Chapter 6 RDF Schema ■ Chapter 7 RDFS-Plus ■ Chapter 8 Using RDFS-Plus in the Wild ■ Chapter 9 Basic OWL ■ Chapter 10 Counting and Sets in OWL ■ Chapter 11 Using OWL in the Wild ■ Chapter 12 Good and Bad Modeling Practices ■ Chapter 13 OWL Levels and Logic

Semantic Web for the Working OntologistDean Allemang, Jim Hendler Chapter 1 What is the Semantic Web? ■ 1. What Is a Web? ■ 2. Smart Web, Dumb Web 2.1. Smart Web Applications 2.2. A Connected Web Is a Smarter Web ■ 3. Semantic Data 3.1. A Distributed Web of Data 3.2. Features of a Semantic Web 3.3. What about the Round-Worlders? 3.4. To Each Their Own 3.5. There’s Always One More 3

Semantic Web for the Working OntologistDean Allemang, Jim Hendler Introduction ■ This book is about something we call the Semantic Web ■ “Semantics” has a number of meanings In what sense are we using the word semantics? How can it be applied to the Web? ■ The aim of this book motivate or pitch the Semantic Web provide the tools necessary for working with it describe the craft of building Semantic Web systems; RDF, RDFS-Plus, OWL.. ▶ coverage of the fundamental tools to show how they can be used together to create Semantic models(Ontologies) 4

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 1. What is a Web? ■ The idea of a web of information ■ Open Community is essential to the notion of the Web Anyone can contribute their ideas for anyone to see It’s Openness resulted in the extensiveness of topics covered by the web But it’s a hodgepodge of different analyses, presentations, and summaries of topics ■ How can we build a more integrated, consistent, deep Web experience? 5 Technical idea accessible only to highly trained; IT admin., librarians, IT architects Anyone to be familiar with Web Widespread adoption of the WWW

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2. Smart Web, Dumb Web ■ Dumb Web means inconsistent, out of synch, and disconnected 6 National Park WebsiteMongotel Website It has mongotel branch informationIt doesn’t have mongotel branch information

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2. Smart Web, Dumb Web ■ Dumb Web means inconsistent, out of synch, and disconnected 7 Astronomy websiteIAU( International Astronomical Union ) Website 9 planets8 planets Pluto is not planet any more

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2.1. Smart Web Applications ■ The Web is full of intelligent applications, with new innovations coming everyday 8 Old Search Engine Recent Search Engine It makes matches that seem deep and intuitive

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2.1. Smart Web Applications ■ The Web is full of intelligent applications, with new innovations coming everyday 9 Old Mapping Site Recent Mapping Site It includes detailed information about world geography and they can plan routes and measure distances

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2.1. Smart Web Applications ■ What is the role of the Web infrastructure in making these applications “smart”? ■ The smarter the infrastructure, the smarter the Web’s performance?  NO! Smart behavior in the Web comes from smart applications on the Web, not from the infrastructure ■ The reason we are improving the Web infrastructure To allow smart applications to perform to their potential ▶ Inconsistent input will still result in confusing “dumb” results, even from smart applications Not to make a web infrastructure that is as smart as possible To make a web infrastructure that is most appropriate to the job of integrating information on the web 10

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2.1. Smart Web Applications ■ The Semantic Web doesn’t need smart data (and it doesn’t make data smart) ■ The Semantic Web just needs to get the right data to the right place So the smart applications can do their work 11 “How can we make the Web infrastructure smarter?” “What can the Web infrastructure provide to improve the consistency and availability of Web data?”

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 2.2. A Connected Web Is a Smarter Web ■ Web data don’t have to be smart → A Connected Web seems smarter ■ We don’t need a smart Web infrastructure ■ But we need a Web infrastructure that lets us connect data to smart Web applications Because smart applications can get the data they need 12 National Park WebsiteMongotel Website Mogotel Information OPark Information X National Park WebsiteMongotel Website Mogotel Information OPark Information O Disconnected data “Dumb Web”Connected Web “Smarter Web”

Semantic Web for the Working OntologistDean Allemang, Jim Hendler Astronomy website IAU Website 2.2. A Connected Web Is a Smarter Web ■ Astronomy website need to update consistently It gives a reader confidence that what they are reading reflects the state of knowledge reported in the website 13 9 planets8 planets Disconnected data “Dumb Web”Connected Web “Smarter Web” Astronomy website IAU Website 8 planets

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3. Semantic Data ■ In the previous example, the data describe the presentation of information rather than describe the entities in the world ■ One common way to make Web applications more integrated is to back them up with relational database But it is very unlikely that there could be a single DB driving many pages 14 Astronomy website IAU Website pluto Not same entity, just text typeset Astronomy website IAU Website pluto

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3. Semantic Data ■ Another approach(a bit smarter) is to write program code in a general-purpose language Advantage over a centralized database But it requires special-purpose code to link data 15 Astronomy website IAU Website 9 planets C, Perl, Java, Lisp, Python, XSLT.. 8 planets Program would update data whenever a change is made to a corresponding page 8 planets!

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.1. A Distributed Web of Data ■ Semantic Web takes this idea one step further, applying it to the Web as a whole ■ This single, distributed model of information is the contribution that the Semantic Web infrastructure brings to smarter web 16 Using Global reference (URI) Machine-readable description of the data Using Global Link (URL) Distributed network of pages that can refer to one another RDF Page

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.2. Features of a Semantic Web “Give Me a Voice..” 1) AAA(Anyone can say Anything about Any topic) Slogan ■ In a web of documents, the AAA slogan means anyone can write a page saying whatever they please and publish it to the Web infrastructure 17

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.2. Features of a Semantic Web ■ In the case of the Semantic Web, it means Our data infrastructure has to allow any individual to express a piece of data about some entity in a way that can be combined with information from other sources This requirement sets some of the foundation for the design of RDF ■ Bottom-up phenomenon Not managed, No administrator With contributions coming from all sources 18

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.2. Features of a Semantic Web “..So I May Speak!” 2) Network Effect: Virtuous Cycle 19 It wasn’t very interesting to be the first kid with a Web server After few people did have Web servers/browsers It became more attractive to have both webpages and Web browsers

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.2. Features of a Semantic Web “..So I May Speak!” 2) Network Effect: Virtuous Cycle ■ Basis of the network effect The more people who are playing, the more attractive it is for new people to start playing (content provide & consume) ■ The Semantic Web has been designed to benefit from the same network effect as more data is available in RDF form, it becomes more useful to write applications that utilize this distributed data 20

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.3. What about the Round-Worlders? ■ For the Network Effect, we have to be prepared to cope with a wide range of variance in the information on the Web ■ Speakers on the Web may disagree ■ 1) They may fundamentally disagree on some topic While the IAU has changed its definition of planet in such a way that Pluto is no longer include, many astrologers have decided to continue to consider Pluto as a planet 21 IAU 8 planets astrologers 9 planets!

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.3. What about the Round-Worlders? ■ 2) Someone might want to intentionally deceive Someone who markets posters, models, or other works that depict nine planets has a good reason to delay reporting the result from the IAU 22 IAU 8 planets 9 planets!

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.3. What about the Round-Worlders? ■ 3) Someone might simply be mistaken Some website might erroneously list Pluto as a planet ■ 4) Some information may be out of date It does take effort to update them 23 IAU 9 planets OLD Website 9 planets

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.4. To Each Their Own: non-unique naming assumption ■ There are many names about the same topic on the Web infrastructure ■ But, coming up with good, agreed-on global names is not always easy business In the absence of such an agreement, different Web authors will select different URIs for the same real-world resource ■ Non-unique naming assumption (feature of the Semantic Web) We have to assume (until told otherwise) tat some Web resource might be referred to using different names by different people (Xena = UB313 = and it could be named other names..) 24 IAUMichael brown Xena UB313 (scientist)

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.5. There’s Always One More: open world assumption ■ We cannot assume that we know everything that has been asserted about one single topic New information be discovered at any time Any one time a particular server that holds information might be unavailable ■ Open world assumption We must assume at any time that new information could come to light 25 National Park Website 10 Mongotels Now there are 13 Mongotels!!

Semantic Web for the Working OntologistDean Allemang, Jim Hendler 3.5. There’s Always One More: open world assumption ■ The Semantic Web includes features that correspond to all the ways of working with open worlds that we have seen in the real world So these techniques allow us to cope with the open world assumption in the Semantic Web 26 National Park WebsiteMongotel Website 4 Mongotels (NY, LA, CA, ME) 2 Mongotels (CA, ME) If this is comprehensive list We can find missing mongotels! “NY, LA”