. . Multi-agent Semantic Web Systems: RDF Models . . . . . Ewan Klein School of Informatics January 30, 2012 . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 1 / 33
. .. seeAlso 1 . .. Motivation for RDF 2 . .. URIs 3 . .. RDF Vocabularies 4 . .. Summary 5 . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 2 / 33
TBL Announcement reported by BBC http://news.bbc.co.uk/1/hi/technology/8470797.stm . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 3 / 33
data.gov.uk/ Beta http://data.gov.uk/ . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 4 / 33
The Semantic Web ’layer cake’ . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 5 / 33
Tabular Data Name Location Stars LovedBy Elephant & Bagel Central **** Bea, Amy Artisan Roast East End ***** Stuey, Rod Peter's Yard Central **** Amy Himalaya Art & Craft Southside *** Rod Vittorio Central **** Stuey . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 6 / 33 Implicit semantics in the arrangement of data Potential issues with multiple values
Relational Data Cafes ID Name Location Stars 1 Elephant & Bagel Central **** 2 Artisan Roast East End ***** 3 Peter's Yard Central **** 4 Himalaya Art & Craft Southside *** 5 Vittoria Central **** LovedBy CafeID Person 1 Bea 1 Amy 2 Stuey 2 Rod 3 Amy 4 Rod 5 Stuey . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 7 / 33
Schema Modification As we add more data, we might want to extend the schema: Cafes & Restaurants ID Name Cuisine Location Stars 1 Elephant & Bagel Central **** 2 Artisan Roast East End ***** 3 Peter's Yard Central **** 4 Himalaya Art & Craft Southside *** 5 Vittoria Italian Central **** 6 Kalpna Indian Southside ***** 7 Nile Valley African Central *** 8 Olive Branch Mediterranean East End ** . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 8 / 33
Distributed Data: Simplified Relational Table Cafes ID Name Location Stars 1 Elephant & Bagel Central **** 2 Artisan Roast East End ***** 3 Peter's Yard Central **** 4 Himalaya Art & Craft Southside *** 5 Vittoria Central **** . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 9 / 33
The Web works though anyone being (technically) allowed to say anything about anything. What the Semantic Web isn’t but can represent (1998) AAA (Tim Berners-Lee) Anyone can say Anything about Anything . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 10 / 33
AAA (Tim Berners-Lee) Anyone can say Anything about Anything The Web works though anyone being (technically) allowed to say anything about anything. What the Semantic Web isn’t but can represent (1998) . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 10 / 33
Distributed Data: Rows Server1 1 Elephant & Bagel Central **** 2 Artisan Roast East End ***** Server2 3 Peter's Yard Central **** Server3 4 Himalaya Art & Craft Southside *** 5 Vittoria Central **** . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 11 / 33
Distributed Data: Columns Name Location Elephant & Bagel Central Artisan Roast East End Peter's Yard Central Server1 Server2 Himalaya Art & Craft Southside Vittoria Central Stars **** ***** **** Server3 *** **** . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 12 / 33
The Web works though anyone being (technically) allowed to say anything about anything. This means that a relationship between two objects may be stored apart from any other information about the two objects. What the Semantic Web isn’t but can represent (1998) AAA (Tim Berners-Lee) Anyone can say Anything about Anything . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 13 / 33
This means that a relationship between two objects may be stored apart from any other information about the two objects. AAA (Tim Berners-Lee) Anyone can say Anything about Anything The Web works though anyone being (technically) allowed to say anything about anything. What the Semantic Web isn’t but can represent (1998) . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 13 / 33
AAA (Tim Berners-Lee) Anyone can say Anything about Anything The Web works though anyone being (technically) allowed to say anything about anything. This means that a relationship between two objects may be stored apart from any other information about the two objects. What the Semantic Web isn’t but can represent (1998) . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 13 / 33
Distributed Data: Cells Server1 Name 1 Elephant & Bagel Server2 Stars Location 4 *** 3 Central Server3 Name 5 Vittoria . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 14 / 33
Cells as Triples name "Elephant & Bagel" E&B location Central PY name "Vittoria" V stars 3 HA&C . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 15 / 33
Cafes Relation Again Cafes ID Name Location Stars 1 Elephant & Bagel Central **** 2 Artisan Roast East End ***** 3 Peter's Yard Central **** 4 Himalaya Art & Craft Southside *** 5 Vittoria Central **** . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 16 / 33
Cafe Graph 4 Vittoria stars location Central location 5 Elephant & Bagel location stars stars lovedBy 4 Peter's Yard lovedBy lovedBy Stu lovedBy Bea Amy Rod lovedBy lovedBy lovedBy Himalaya Art & Crafts location East End location Southside Artisan Roast stars stars 5 3 . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 17 / 33
Knows Graph knows knows Stu Bea Amy . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 18 / 33
Merging Two Graphs 4 Vittoria stars location Central location 5 Elephant & Bagel location stars stars lovedBy 4 Peter's Yard lovedBy lovedBy knows Stu lovedBy knows Bea Amy Rod lovedBy lovedBy lovedBy Himalaya Art & Crafts location East End location Southside Artisan Roast stars stars 5 3 . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 19 / 33
What do HTTP URIs Identify? In RDF, URIs identify resources, they do not retrieve them. Not every resource has a digital representation. http://homepages.inf.ed.ac.uk/ewan/index.html — does this identify ▶ me, or ▶ a document about me? Alternative suggestion (cf. assignment 1): http://homepages.inf.ed.ac.uk/ewan/foaf.rdf#ehk http://www.inf.ed.ac.uk/ontology#hip-hop will trigger a 404 Not Found response, but it is a valid URI. . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 20 / 33
URI References and Fragment Identifiers, 1 A URI Reference (URIref) is a URI with an optional fragment identifier at the end: . URI with Fragment Identifier . . . scheme domain path fragment � �� � � �� � � �� � ���� http :// www . inf . ed . ac . uk / ontology# annotation . . . . . . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 21 / 33
URI References and Fragment Identifiers, 2 Fragment identifiers commonly used to identify specific locations in HTML documents: . Fragments in HTML Pages . . . http://www.example.com/index.html http://www.example.com/index.html#Section2 . . . . . In RDF, the two URIs above are independent identifiers. URIs with fragment identifiers commonly called hash URIs . . . . . . Ewan Klein (School of Informatics) Multi-agent Semantic Web Systems: RDF Models January 30, 2012 22 / 33
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