OpenHPI 2.1 - How to Identify Things - URIs
Upcoming SlideShare
Loading in...5
×

Like this? Share it with your network

Share

OpenHPI 2.1 - How to Identify Things - URIs

  • 1,114 views
Uploaded on

 

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
1,114
On Slideshare
1,114
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
45
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Semantic Web TechnologiesLecture 2: Semantic Web - Basic Architecture I 01: How to Identify Things? - URIs Dr. Harald Sack Hasso Plattner Institute for IT Systems Engineering University of Potsdam Spring 2013 This file is licensed under the Creative Commons Attribution-NonCommercial 3.0 (CC BY-NC 3.0)
  • 2. 2Lecture 2: Semantic Web - Basic Architecture I Open HPI - Course: Semantic Web Technologies Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 3. 2. Semantic Web - Basic Architecture Part 13 Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 4. 4 01 How to Identify Things? - URIsOpen HPI - Course: Semantic Web Technologies - Lecture 2: Semantic Web Basic Architecture I Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 5. What is this?5 Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 6. What`s the difference?6 Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 7. Semiotic Triangle7 Concept symbolizes refers to Symbol Object stands for „apple“ Ogden, Richards: Semiotic Triangle, 1923 Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 8. Semiotic Triangle7 shared concept Concept symbolizes refers to Symbol Object stands for „apple“ Ogden, Richards: Semiotic Triangle, 1923 Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 9. The Designator in the Web8 Uniform □ different types of resource identifiers all constructed according to a uniform schema Resource □ whatever may be identified via URI Identifier □ to distinguish one resource from another Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 10. Uniform Resource Identifier9 ■ A Uniform Resource Identifier (URI) defines a simple and extensible schema for worldwide unique identification of abstract or physical resources (RFC 3986). ■ Resource can be every object with a clear identity (according to the context of the application) □ as e.g., web pages, books, locations, persons, relations among objects, abstract concepts, etc. ■ The concept of URI is already established in various domains, as e.g., □ the Web (URL, PRN, pURL), □ Books and publications (ISBN, ISSN), □ Digital Object Identifier (DOI) Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 11. URI, Resource and Resource Representation10 URI http://www.tour-eiffel.fr/index.html identifies representation represents (stands for) Metadata: Content-type: text/html Data: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <title>Le site officiel de la Tour Eiffel</title> ... </html> Eiffel Tower Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 12. Representation and Presentation11 Metadata: Content-type: text/html Data: defines <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> Presentation <head> <title>Le site officiel de la Tour Eiffel</title> ... </html> Representation Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 13. HTTP Request / Response12 Browser sends HTTP Request GET http://www.tour-eiffel.fr/index.html HTTP/1.1 Host: www.tour-eiffel.fr Accept: text/htmlUser clicks Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 14. HTTP Request / Response13 Browser sends HTTP Request Web Server processes request GET http://www.tour-eiffel.fr/index.html HTTP/1.1 Host: www.tour-eiffel.fr Accept: text/html Browser interprets representation and displays presentation Web Server sends HTTP Response HTTP/1.1 200 OK Content-Length: 3134 Web Server of Content-Type: text/html; charset=utf-8 www.tour-eiffel.fr <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <title>Le site officiel de la Tour Eiffel</title> ... </html> Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 15. Designator and Designatum Designatum14 Designator ≠ The web page describes (designates) the Eiffel Tower The Eiffel Tower is described (designated) by the web page Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 16. 2. Semantic Web Basisarchitektur 2.1 Uniform Resource Identifier - URI15 Bezeichner und Bezeichnetes René Magritte: Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam La trahison des images (1928)
  • 17. 16 Johannes Osterhoff:: Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam La trahison des pommes (2011)
  • 18. Designator and Designatum17 The distinguishing characteristic of [information] resources is that all of their essential characteristics and can be conveyed in a message. W3C: Architecture of the World Wide Web, Volume One □ A resource can be described (designated) via Metadata □ Even if the resource itself cannot be delivered from the web server, probably its representation might be available that describes the resource sufficiently. Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 19. 18 Metadata Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 20. URI, Ressource and Metadata19 URI http://www.tour-eiffel.fr/index.html identifies Resource: Eiffel Tower Representation describes (designates) Metadata: Content-type: text/html Data: <!DOCTYPE HTML PUBLIC "-//W3C//DTD represents HTML 4.01 Transitional//EN" Information about Resource: "http://www.w3.org/TR/html4/loose.dtd"> the Eiffel Tower Eiffel Tower <html> (stands for) <head> Metadata <title>Le site officiel de la Tour Eiffel</title> ... </html> Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 21. Uniform Resource Identifier20 ■ URI combines Address □ Address (Locator) □ Uniform Resource Locator (URL, RFC 1738) □ denotes, where a resource can be found in the Web by stating its primary access mechanism □ might change during life cycle □ Identity (Name) Name □ Uniform Resource Name (URN, RFC 2141) □ persistent identifier for a Web resource □ remains unchanged during life cycle Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 22. URI - Generic Syntax21 ■ US-ASCII Encoding ■ Percent Encoding for reserved characters, or characters that do not exist in US-ASCII encoding existieren pct-encoded = "%" HEXDIG HEXDIG ■ Reserved characters with special function reserved = gen-delims / sub-delims gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@“ sub-delims = "!" / "$" / "&" / "" / "(" / ")" / "*" / "+" / "," / ";" / "=" ■ Permitted characters unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~" ■ Extension to Universal Character Code (Unicode/ISO 10646) □ Internationalized Resource Identifier (IRI, RFC 3987) e.g.: Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 23. URI - Generic Syntax22 URI = schema"://"[userinfo"@"]host[:port][path]["?"query]["#"fragment] ■ schema: e.g. http, ftp, mailto,... ■ userinfo: e.g. username:password ■ host: e.g. Domain-Name, IPv4/IPv6 Address ■ port: e.g. :80 for standard http port ■ path: e.g. path in file system of WWW server ■ query: e.g. parameters to be passed over to applications ■ fragment: e.g. determines a specific fragment of a document Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 24. URIs in the Semantic Web23 ■What if a URI for a resource does not exist? ■ Define a URI by yourself: □ avoid overlaps  use your own website □ enables documentation at the same place ( Content Negotiation) ■ Separate URI for resource (Designatum) and its documentation (Designator) via URI references (i.e. via "#" fragments) or Content Negotiation z.B.: http://hpi.uni-potsdam.de/harald_foaf.rdf#me Sauermann, Cyganiak: Cool URIs for the Semantic Web, W3C Interest Group Note 03 December 2008, http://www.w3.org/TR/cooluris/ Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 25. 24Lecture 2: Semantic Web - Basic Architecture I Open HPI - Course: Semantic Web Technologies Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  • 26. 24Lecture 2: Semantic Web - Basic Architecture I Open HPI - Course: Semantic Web Technologies Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam