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1OReilly Enterprise Java Conference, 2001An Introduction to RDF.

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Presentation on theme: "1OReilly Enterprise Java Conference, 2001An Introduction to RDF."— Presentation transcript:

1 1OReilly Enterprise Java Conference, 2001An Introduction to RDF

2 2OReilly Enterprise Java Conference, 2001An Introduction to RDF Facilities to put machine-understandable data on the Web are becoming a high priority for many communities. The Web can reach its full potential only if it becomes a place where data can be shared and processed by automated tools as well as by people. For the Web to scale, tomorrow's programs must be able to share and process data even when these programs have been designed totally independently. The Semantic Web is a vision: the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications.

3 3OReilly Enterprise Java Conference, 2001An Introduction to RDF History

4 4OReilly Enterprise Java Conference, 2001An Introduction to RDF What is the Web, Really ? Millions upon millions of computers all using the same communications protocol TCP/IP HTTP HTML

5 5OReilly Enterprise Java Conference, 2001An Introduction to RDF HTML DEPARTMENT OF MATHEMATICS AND COMPUTER SCIENCE SAN JOSE STATE UNIVERSITY SPRING 2000 COLLOQUIUM SERIES, PART II Each talk with be on a Thursday at 3:00 p.m. in MacQuarrie Hall 523 Please join us for refreshments beforehand, at 2:30 p.m., in MacQuarrie Hall 210 Parking available in the Seventh Street Garage at South Seventh and San Salvador Streets, San Jose, CA April 6 Zvezdelina Stankova-Frenkel, Mathematics, Mills College From Desargues to Modern Algebraic Geometry We will look at some classical plane geometry... mathematics.

6 6OReilly Enterprise Java Conference, 2001An Introduction to RDF The Evolution of Web Technology HTML 1.0 became 2.0 became... 4.0 Cascading style sheets and other formatting and layout standards defined by W3C Proprietary technologies such as Shockwave and PDF invented

7 7OReilly Enterprise Java Conference, 2001An Introduction to RDF The Implicit Assumptions Point to point (direct) communication The primary task of a web server is to deliver information to a human who is asking for that information –Key points: to a human, already asking for information

8 8OReilly Enterprise Java Conference, 2001An Introduction to RDF The First Business Opportunity The Web is like mail-order Put Catalogs on the web –Easy to update –Easy to link in auxiliary information People who bought that also bought … Availability information In many cases, simply putting an HTML front end on existing systems

9 9OReilly Enterprise Java Conference, 2001An Introduction to RDF Leads to Another Opportunity Catalogs prime the pump –Easy to understand application that is compelling –Side-effect: lots of information is now available on the internet How do we take advantage of it ? –Automate existing processes –Enable new applications

10 10OReilly Enterprise Java Conference, 2001An Introduction to RDF HTML is a Problem Its a markup language based on document structure –Most tags are visual, about presentation –HTML solves document-level navigation problems, for humans –Lots of information encoded in images Fundamentally, the wrong idea.

11 11OReilly Enterprise Java Conference, 2001An Introduction to RDF eXtensible Markup Language (XML) Basically, a language for defining markup languages Key idea: separate data from presentation information Replace HTML with two things A domain specific markup language (defined in XML) A map from that markup language to HTML (defined using XSL)

12 12OReilly Enterprise Java Conference, 2001An Introduction to RDF Split Data 1998 National League East Atlanta Braves Malloy Marty Second Base 11 8 28 3 5 1..... Meaning! From: The XML Bible by Harold

13 13OReilly Enterprise Java Conference, 2001An Introduction to RDF From Presentation Major League Baseball Statistics Major League Baseball Statistics Formatting!

14 14OReilly Enterprise Java Conference, 2001An Introduction to RDF What is the Web, XML Version HTML is a tag language, defined using XML –One of many tag languages (and the likely target for XSL transformations) TCP/IP HTTP XML XHTMLSpecial Purpose Tag Languages

15 15OReilly Enterprise Java Conference, 2001An Introduction to RDF XML Has Lots of Problems Everything bottoms out in strings DTDs provide simple structure at the level of documents –Very simple inter-document structure –No provisions for intra-document structure No support for versioning

16 16OReilly Enterprise Java Conference, 2001An Introduction to RDF The VISA DTD

17 17OReilly Enterprise Java Conference, 2001An Introduction to RDF It Gets Worse

18 18OReilly Enterprise Java Conference, 2001An Introduction to RDF The Accompanying Prose The DTD is 4 pages The manual is 182 pages The aim of this Guide is to provide sufficient information about the XML Invoice Document to enable its implementation. It documents the file structure, the business usage of the elements, and all the elements and attributes in detail.

19 19OReilly Enterprise Java Conference, 2001An Introduction to RDF RDF

20 20OReilly Enterprise Java Conference, 2001An Introduction to RDF Goal: The Semantic Web Different sites each maintain small amounts of information Sites need to refer to each others information with full semantic integrity –Information is maintained by owners and referred to by other sites –Information should be accessible, and coherent, in very small chunks

21 21OReilly Enterprise Java Conference, 2001An Introduction to RDF Needed: Precision Need the ability to specify things like dates, times, and monetary amounts Compile in those VISA comments –The more of this we can do, the less programmer-hours are needed Ultimately, most web-based computation will not involve a browser

22 22OReilly Enterprise Java Conference, 2001An Introduction to RDF Needed: Granularity Saying things at the page level is too coarse grained Small chunks of data necessary –And ability to aggregate into larger chunks important

23 23OReilly Enterprise Java Conference, 2001An Introduction to RDF Use Classes and Instances Objects are a natural way to represent information A web page can contain hundreds of instances, each with its own URI Hard part is figuring out how to do this in a way that works on the web

24 24OReilly Enterprise Java Conference, 2001An Introduction to RDF Start with Resources A resource is a thing you talk about (can reference) Everything is a resource Resources have URIs

25 25OReilly Enterprise Java Conference, 2001An Introduction to RDF How to say things in RDF Small set of canonical tags Use XML syntax to define vocabularies Information asserted via triples –Assertions require three things: Subject: What the assertion is about (always a resource) Property: A property whose value is being asserted (always a resource) Object: The value of the property (either a resource or a primitive value)

26 26OReilly Enterprise Java Conference, 2001An Introduction to RDF Important Tags rdf:Description rdfs:Class rdfs:Property rdf:type rdfs:subClassOf rdfs:domain rdfs:range

27 27OReilly Enterprise Java Conference, 2001An Introduction to RDF Defining a Class

28 28OReilly Enterprise Java Conference, 2001An Introduction to RDF An Instance of Motor Vehicle

29 29OReilly Enterprise Java Conference, 2001An Introduction to RDF Resources Define Tags

30 30OReilly Enterprise Java Conference, 2001An Introduction to RDF Classes Object-oriented notion There are classes, arranged in a taxonomy (with subclass relationships) Instances can be instances of more than one class

31 31OReilly Enterprise Java Conference, 2001An Introduction to RDF Adding a Property

32 32OReilly Enterprise Java Conference, 2001An Introduction to RDF Setting Property Values 47

33 33OReilly Enterprise Java Conference, 2001An Introduction to RDF Properties Similar to fields (data members, attributes...) Big difference: theyre first class objects –Defined independently of classes –Asserted independently of classes Classes dont come with a set of data members Other people (other pages) can assert properties about your classes and instances without your knowledge or permission

34 34OReilly Enterprise Java Conference, 2001An Introduction to RDF The Web of Knowledge Corning Fiberglass has a product catalog Home Appliances Defines things like Blender Sears has an on-line store that uses (and extends) both of these as standard vocabularies Corning Fiberglass has a product catalog Corning Fiberglass has a product catalog Corning Fiberglass has a product catalog

35 35OReilly Enterprise Java Conference, 2001An Introduction to RDF The Web of Knowledge Public Opinion And Ratings Terminology Corning Fiberglass has a product catalog Home Appliances. Defines things like Blender Sears has an on-line store that uses (and extends) both of these as standard vocabularies Corning Fiberglass has a product catalog Corning Fiberglass has a product catalog Corning Fiberglass has a product catalog Consumer Reports uses the product catalogs and attaches more information to them

36 36OReilly Enterprise Java Conference, 2001An Introduction to RDF What is the Web, RDF Version Usually called The Semantic Web TCP/IP HTTP XML RDF and RDF-Schema Schema Instances

37 37OReilly Enterprise Java Conference, 2001An Introduction to RDF Further Information http://www.w3.org/RDF/ http://www.w3.org/2001/sw/ http://www.semanticweb.org/ http://www.mozilla.org/rdf/doc/ http://www.xml.com/pub/a/2001/01/24/rdf. html http://xml.coverpages.org/rdf.html

38 38OReilly Enterprise Java Conference, 2001An Introduction to RDF Programmatic Resources Protege (http://www smi.stanford.edu/projects/protege) RDF DB (http://web1.guha.com/rdfdb/) Redland (http://www.redland.opensource.ac.uk/) Java API (http://www- db.stanford.edu/~melnik/rdf/api.html) Squish (http://swordfish.rdfweb.org/rdfquery/)

39 39OReilly Enterprise Java Conference, 2001An Introduction to RDF High Profile Uses Electric Power Industry (http://www.langdale.com.au/XMLCIM.ht ml) DMOZ (http://www.dmoz.org/) Epinions (http://www.epinions.com) DAML (www.daml.org)


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