The Semantic Web Made Simple

1. The Semantic Web Made Simple David Price December 2004 david.price@eurostep.com

2. Agenda • The Current Web • and its technologies • How’s it work now? • The Semantic Web • is adding semantics • How’s it going to work in the future?

3. The Current Web • Web core concepts • People read Web pages • Web page authors can control basic layout • Web pages need to link to each other • Web pages need to link to online media • that people read, view, listen to or interpret • People use tools that search/recall Web content (Yahoo, Google, Lycos, their own bookmarks)

4. What’s on a Web Page? Categories of articles Text that’s actually graphics Online shopping link Article title and link A photograph Date and time Article abstract Location, temperature and unit

5. What we saw • Things on the NY Times site • Text that’s actually a graphic • Categories of articles • Online shopping link • A photograph • Article title and link • Article abstract • Date and time • Location, temperature and unit • How did we know that? • Because we are humans who can read English and who can interpret what we see

6. What did the editors do? • Determined the layout of the pages as a whole • Should it look like a real paper? Should there be advertising? • Wrote the text • Decided on navigation • Articles categories called “International”, “National”, “Sports”, etc. • Article categories list items link to separate page for each category with list of articles • Users will have to scroll down the page to see the headline articles • Articles titles will link directly to separate page for each article

7. How did they do that? • They used HTML and graphic images • Hypertext Markup Language (HTML) allows editors to • control presentation and layout • Paragraph, Bold, Table/Column/Row • add links to other pages • Hyperlink Reference • show graphics • Image of many types are natively supported by browsers • link to other media that have software to present them • music, video, PDF, documents, presentations

8. A peek under the covers

9. How does that work? • HTML is a standard language • World Wide Web consortium standardized it • Companies have written software that reads HTML and presents it to you • These are Web browsers • The presentation capabilities of HTML, the related media and browsers are pretty powerful

10. How does HTML really work? • What do the browsers understand? • <P>This is a paragraph.</P> • Present the text “This is a paragraph.” as a new paragraph • <A HREF=“newsitems.html”>News</A> • Present a hyperlink of text “News” and if it’s selected present new page from file “newsitems.html” • <TR><TD>dog</TD><TD>cat</TD><TR> • In the current row of the table, present text “dog” in column 1 of table and text “cat” in column 2 of table • <IMG SRC=“p1.jpg” /> • Present an image from whatever is in the file named “p1.jpg”

11. So, What’s the problem? • Only a human being can read a Web page and extract any meaning from it • The Web browser does understand paragraph, image, link • The Web browser does not know it’s linking to a “News Article” or the image is a “picture of photographs” • It’s the meaning that’s really important • Wouldn’t it be powerful if computers could get some of the meaning out of Web pages?

12. Why is it a powerful idea? • Using our NY Times/newspaper site example… • Suppose you were an Environmental Group • Suppose you want to monitor news stories about the environment or pollution • You could write a program that searches the Web media outlets • That program could trigger a notification about articles on environmental issues • Or, it could contact members of your group in specific locations when it finds legislation related to pollution in particular US states • This would save your members a lot of time searching for themselves, wouldn’t it?

13. The Semantic Web • Figuring out how to get meaning out of things on the Web using software is what “The Semantic Web” is all about • “using software” means “without humans doing the interpretation” • How would one do that? • Clearly, HTML is not sufficient, so more powerful languages are required • Clearly, cannot replace everything already on the Web, so ways to add meaning are required • Need to combine better languages/communication, computer science and the study of what things mean

14. Semantics • People have been studying what things exist and what they mean for centuries • This is called Philosophy • People have been studying how people communicate for decades • This is called Linguistics • People have been studying how computers can “learn” for a few decades • This is called Artificial Intelligence

15. The Semantic Web • Vision of Web “inventer” Tim Berners-Lee and others • Wrote an article in Scientific American in 2001 • Goals • Go beyond processing by human beings • Make Web content computer processable • How? • Add semantics using ontologies • Use inference/reasoning over ontologies

16. Ontologies • Ontology • A big word from philosophy, linguistics, and computer science • A formal, machine readable specification of a domain of interest • Names things and adds knowledge about and constraints on the things • Allows relationships between terms within and between different ontologies • Semantic Web researchers and W3C have been working several years now

17. OWL History • US researchers produced DAML-ONT in 2000 • DARPA Agent Markup Language – Ontology Language • European researchers produced OIL about the same time • Ontology Inference Layer • Merged to produce DAML+OIL and submitted as Note to W3C and formed the W3C WebOnt group in 2001 • W3C WebOnt Group produced OWL in 2003 • OWL is now a W3C Recommendation • This is not really that important for our purposes… just remember that OWL didn’t appear overnight

18. What is OWL? • The World Wide Web Consortium (W3C) created the HTML and XML standards • OWL is a next-generation W3C Web standard • its purpose is to add “semantics” to the Web • Therefore, it can be distributed and is Web-enabled and does not assume a single source for everything • In concept, it is very much like other data modelling languages (it calls models or schemas “ontologies”) • class, subclass, property, property type, instance/individual • supports set theory and logic-based statements about the classes and individuals • it has more than one syntax, XML being one

19. RDF underlies OWL • RDF is another W3C standard, the Resource Description Framework • RDF is simple in concept but sufficient for many basic Semantic Web tasks (e.g. who created this presentation?) • It allows you to assign a property with a value to a Web page (or any Web resource)

20. http://www.eurostep.com/TheSemanticWeb.ppt Creator “David Price” RDF underlies OWL • RDF is another W3C standard, the Resource Description Framework • RDF is simple in concept but sufficient for many basic Semantic Web tasks (e.g. who created this presentation?) • RDF is often represented by nodes and arcs

21. Back to the NY Times

22. What we saw… again • Things on the NY Times site • Text that’s actually a graphic • Categories of articles • Online shopping link • A photograph • Article title and link • Article abstract • Date and time • Location, temperature and unit • How did we know that? • Because we are humans who can read English and who can interpret what we see

23. A peek under the semantic covers Article title Newspaper ontology Article Authors Date Article Subjects

24. Without using an editor … Now these are semantics a software application can understand… Articles and Authors

25. On Annotating the Web • You might ask: But what about the current Web content, we’re not going to rewrite it all are we? • And we’d answer: Of course not, but you can “annotate” them to add semantics. • What this means is: • Descriptive ontologies like the one for Newpapers are being developed • Descriptions are then linked to already existing Web pages, including any multi-media content (e.g. video) • The Semantic Web community calls this “annotating a Web resource” • You’ll also hear people use the term “metadata” too

26. So, How does OWL Work? • An Ontology • is a formal description of a field of interest • defines Classes – the kinds of things of interest • Article, Person, etc. • defines Properties – the relationships and characteristics related to Classes • Article is WrittenBy Person, Person has Name • Then, based on the Ontology people create content • An author writes articles using software that understands the Newspaper Ontology • The Publisher gathers all the articles, classifieds, etc. and links them into the online version of the NY Times

27. But how does that help? • If everyone, or at least a reasonably large community, agreed on an ontology for Newspapers • then sharing articles between sites is possible • presentation can be layered on top of the semantic content of the articles • Web robots, only smarter than Google, can find and relate content about specific subjects, by specific authors, etc. • The key is getting agreement on the ontologies • This is ongoing in various standards bodies, consortia, etc. but remains a major issue for the Semantic Web

28. In Conclusion • The Semantic Web goal is to make semantic content of Web pages available for software applications • Work has been ongoing for several years • Building on decades of research • The OWL language is a key development • As are the languages upon which it is based, such as RDF Schema • But that’s for another day…