The Semantic Web #4 - RDF (1)
Download as PPTX, PDF0 likes1,064 views
The document discusses the Resource Description Framework (RDF) and its applications in linked data and semantic web technologies, emphasizing the need for structured data representation. It covers key components including syntax, URIs for identifying subjects, predicates, and objects, and the use of XML for machine-processable data. The document also details the concept of triples, blank nodes, and how RDF statements can model complex relationships.
![Defining Base URI
• XML Base
– facility for defining base URIs for parts of XML documents
– to specify a base URI other than the base URI of the document or external
entity
1. <?xml version="1.0"?>
2. <!DOCTYPE rdf:RDF [<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#">]>
3. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
4. xmlns:exterms="http://www.example.com/terms/"
5. xml:base="http://www.example.com/2002/04/products">
6. <rdf:Description rdf:about="#item10245">
7. <exterms:model rdf:datatype="&xsd;string">Overnighter</exterms:model>
8. <exterms:sleeps rdf:datatype="&xsd;integer">2</exterms:sleeps>
9. </rdf:Description>
10. </rdf:RDF>
exterms:model
“Overnighter”^^&xsd;string
http://www.example.com/2002/04/products#item10245
exterms:sleeps 2^^&xsd;integer
28
Linked Data & Semantic Web Technology](https://image.slidesharecdn.com/thesemanticweb04-130326213849-phpapp01/85/The-Semantic-Web-4-RDF-1-28-320.jpg)
![rdf:ID Attribute
• rdf:ID Attribute
– to specify a fragment identifier, given by the value of the rdf:ID
attribute
– interpreted relative to a base URI appending the character "#"
1. <?xml version="1.0"?>
2. <!DOCTYPE rdf:RDF [<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#">]>
3. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
4. xmlns:exterms="http://www.example.com/terms/"
5. xml:base="http://www.example.com/2002/04/products">
6. <rdf:Description rdf:ID="item10245">
7. <exterms:model rdf:datatype="&xsd;string">Overnighter</exterms:model>
8. <exterms:sleeps rdf:datatype="&xsd;integer">2</exterms:sleeps>
9. </rdf:Description>
10. </rdf:RDF>
exterms:model
“Overnighter”^^&xsd;string
http://www.example.com/2002/04/products#item10245
exterms:sleeps 2^^&xsd;integer
29
Linked Data & Semantic Web Technology](https://image.slidesharecdn.com/thesemanticweb04-130326213849-phpapp01/85/The-Semantic-Web-4-RDF-1-29-320.jpg)
The Semantic Web #4 - RDF (1)
- 1. Linked Data & Semantic Web Technology The Semantic Web Part 4. Resource Description Framework (1) Dr. Myungjin Lee
- 2. Problem of XML • Park Ji Sung has the phone number (+82)-10-3099-9183. <person> <name>Park Ji Sung</name> <tel>(+82)-10-3099-9183</tel> </person> <person name=“Park Ji Sung”> <tel>(+82)-10-3099-9183</tel> </person> <person name=“Park Ji Sung” tel=“(+82)-10-3099-9183” /> We need a method to represent data on abstract level. 2 Linked Data & Semantic Web Technology
- 3. Problem of XML • Park Ji Sung has the phone number (+82)-10-3099-9183. <person> <name>Park Ji Sung</name> <tel>(+82)-10-3099-9183</tel> </person> <Human> <Name>Park Ji Sung</Name> <CellPhoneNumber>(+82)-10-3099-9183</CellPhoneNumber> </Human> <Friend> <Name>Park Ji Sung</Name> <Phone>(+82)-10-3099-9183</Phone> </Friend> We need a method to represent semantics of data. 3 Linked Data & Semantic Web Technology
- 4. Basic Concept of Knowledge Representation • http://www.example.org/index.html has a creator whose value is John Smith http://www.example.org/index.html creator John Smith – the thing the statement describes (the Web page, in this case) – a specific property (creator, in this case) of the thing the statement describes – the thing the statement says is the value of this property (who the creator is), for the thing the statement describes • intuitive knowledge representation with directed graph 4 Linked Data & Semantic Web Technology
- 5. RDF (Resource Description Framework) • to be used as a general method for conceptual description or modeling of information that is implemented in web resources, using a variety of syntax notations and data serialization formats • based on the idea that the things being described have properties which have values, and that resources can be described by making statements 5 Linked Data & Semantic Web Technology
- 6. Terminology for the Various Parts of Statements • http://www.example.org/index.html has a creator whose value is John Smith http://www.example.org/index.html creator John Smith – the subject is the URL http://www.example.org/index.html – the predicate is the word "creator" – the object is the phrase "John Smith" 6 Linked Data & Semantic Web Technology
- 7. Two Things for Processing by Machines • a system of machine-processable identifiers for identifying a subject, predicate, or object in a statement without any possibility of confusion with a similar-looking identifier that might be used by someone else on the Web. Use URI (Uniform Resource Identifier) • a machine-processable language for representing these statements and exchanging them between machines. Use XML syntax 7 Linked Data & Semantic Web Technology
- 8. Use URIs • RDF uses URIs as the basis of its mechanism for identifying the subjects, predicates, and objects in statements. • URI references (URIref) – a URI, together with an optional fragment identifier at the end – http://www.example.org/index.html#section2 8 Linked Data & Semantic Web Technology
- 9. Use the XML Syntax • To represent RDF statements in a machine-processable way, RDF uses the Extensible Markup Language. • RDF/XML – for use in representing RDF information, and for exchanging it between machines – <contact:fullName> and <contact:personalTitle> to delimit the text content Eric Miller and Dr. 9 Linked Data & Semantic Web Technology
- 10. Statements • English Statement – http://www.exaple.org/index.html has a creator whose value is John Smith • RDF Statement – a subject http://www.example.org/index.html – a predicate http://purl.org/dc/elements/1.1/creator – and an object http://www.example.org/staffid/85740 • RDF Graph Model – a node for the subject – a node for the object – an arc for the predicate, directed from the subject node to the object node 10 Linked Data & Semantic Web Technology
- 11. Groups of Statements • http://www.example.org/index.html has a creation-date whose value is August 16, 1999 • http://www.example.org/index.html has a language whose value is English 11 Linked Data & Semantic Web Technology
- 12. Triple • an alternative way of writing down the statements • written as a simple triple of subject, predicate, and object, in that order <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/creator> <http://www.example.org/staffid/85740> . <http://www.example.org/index.html> <http://www.example.org/terms/creation-date> "August 16, 1999" . <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/language> "en" . 12 Linked Data & Semantic Web Technology
- 13. Shorthand Way of Writing Triples • QName (XML Qualified Name) – a valid identifier for elements and attributes – a prefix that has been assigned to a namespace URI, followed by a colon, and then a local name • For Example, – prefix dc:, namespace URI: http://purl.org/dc/elements/1.1/ – prefix ex:, namespace URI: http://www.example.org/ – prefix exterms:, namespace URI: http://www.example.org/terms/ – prefix exstaff:, namespace URI: http://www.example.org/staffid/ ex:index.html dc:creator exstaff:85740 . ex:index.html exterms:creation-date "August 16, 1999" . ex:index.html dc:language "en" . 13 Linked Data & Semantic Web Technology
- 14. Structure of Statements http://semantics.kr/rel/hasWife http://semantics.kr/myungjinlee http://semantics.kr/hye-jinhan Subject Predicate Object URI reference URI reference URI reference or Literal Statement 14 Linked Data & Semantic Web Technology
- 15. URIref and Literal • URIref – to identify the things – shown as ellipses – not only the subject of the original statement, but also the predicate and object • Literal – constant values represented by character strings – shown as boxes – Literals may not be used as subjects or predicates in RDF statements. 15 Linked Data & Semantic Web Technology
- 16. Literal • Plain Literal – a string combined with an optional language tag • Types Literal – a string combined with a datatype URI – based on XML Schema datatypes 16 Linked Data & Semantic Web Technology
- 17. XML Schema Datatypes • Namespace of XML Schema – http://www.w3.org/2001/XMLSchema • Datatypes Simple Type Examples string Confirm this is electric integer ...-1, 0, 1, ... long -9223372036854775808, ... -1, 0, 1, ... 9223372036854775807 float -INF, -1E4, -0, 0, 12.78E-2, 12, INF, NaN date 1999-05-31 time 13:20:00.000, 13:20:00.000-05:00 boolean true, false, 1, 0 17 Linked Data & Semantic Web Technology
- 18. Blank Nodes • a way to represent multi-valued relationships • Why we need blank nodes? – structured information consisting of separate values exstaff:85740 exterms:address "1501 Grant Avenue, Bedford, Massachusetts 01730" . exstaff:85740 exterms:address exaddressid:85740 . exaddressid:85740 exterms:street "1501 Grant Avenue" . exaddressid:85740 exterms:city "Bedford" . exaddressid:85740 exterms:state "Massachusetts" . exaddressid:85740 exterms:postalCode "01730" . the node itself provides the necessary connectivity between the various other parts of the graph 18 Linked Data & Semantic Web Technology
- 19. Blank Nodes blank node identifiers, having the form _:name, to indicate the presence of blank nodes exstaff:85740 exterms:address _:johnaddress . _:johnaddress exterms:street "1501 Grant Avenue" . _:johnaddress exterms:city "Bedford" . _:johnaddress exterms:state "Massachusetts" . _:johnaddress exterms:postalCode "01730" . 19 Linked Data & Semantic Web Technology
- 20. Example of Blank Nodes • An actor appears two movies as different roles. movie:appear movie:TomCruise movie:JackReacher movie:appear movie:TopGun movie:role movie:role movie:JackReacher movie:LTPeteMitchell movie:appear movie:JackReacher movie:hasMovie movie:TomCruise movie:role movie:JackReacher movie:hasMovie movie:appear movie:role movie:TopGun movie:LTPeteMitchell Linked Data & Semantic Web Technology
- 21. RDF/XML • RDF/XML – an XML syntax for writing down and exchanging RDF graphs – the normative syntax for writing RDF English Statement http://www.example.org/index.html has a creation-date whose value is August 16, 1999 RDF Graph Triple ex:index.html exterms:creation-date "August 16, 1999" . RDF/XML 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:exterms="http://www.example.org/terms/"> 4. <rdf:Description rdf:about="http://www.example.org/index.html"> 5. <exterms:creation-date>August 16, 1999</exterms:creation-date> 6. </rdf:Description> 7. </rdf:RDF> Linked Data & Semantic Web Technology
- 22. RDF/XML Document Root Element of RDF/XML Document XML Declaration Namespace for RDF Vocabularies 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:exterms="http://www.example.org/terms/"> Element for Description of a Resource Attribute to specify the URIref of the Subject Another XML Namespace Declaration 4. <rdf:Description rdf:about="http://www.example.org/index.html"> 5. <exterms:creation-date>August 16, 1999</exterms:creation-date> 6. </rdf:Description> Subject of Statement Property of Statement Plain Literal Value of Statement 7. </rdf:RDF> RDF Statement 22 Linked Data & Semantic Web Technology
- 23. RDF/XML for Two Statements Triples ex:index.html exterms:creation-date "August 16, 1999" . ex:index.html dc:language "en" . RDF/XML 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:dc="http://purl.org/dc/elements/1.1/" 4. xmlns:exterms="http://www.example.org/terms/"> 5. <rdf:Description rdf:about="http://www.example.org/index.html"> 6. <exterms:creation-date>August 16, 1999</exterms:creation-date> 7. </rdf:Description> 8. <rdf:Description rdf:about="http://www.example.org/index.html"> 9. <dc:language>en</dc:language> 10. </rdf:Description> 11. </rdf:RDF> 23 Linked Data & Semantic Web Technology
- 24. Abbreviating Multiple Properties Triples ex:index.html dc:creator exstaff:85740 . ex:index.html exterms:creation-date "August 16, 1999" . ex:index.html dc:language "en" . RDF Graph RDF/XML 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:dc="http://purl.org/dc/elements/1.1/" 4. xmlns:exterms="http://www.example.org/terms/"> 5. <rdf:Description rdf:about="http://www.example.org/index.html"> 6. <exterms:creation-date>August 16, 1999</exterms:creation-date> 7. <dc:language>en</dc:language> 8. <dc:creator rdf:resource="http://www.example.org/staffid/85740"/> 9. </rdf:Description> 10. </rdf:RDF> Attribute to indicates that the property element's value is another resource 24 Linked Data & Semantic Web Technology
- 25. RDF/XML Describing a Blank Node 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:dc="http://purl.org/dc/elements/1.1/" 4. xmlns:exterms="http://example.org/stuff/1.0/"> 5. <rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar"> 6. <dc:title>RDF/XML Syntax Specification (Revised)</dc:title> 7. <exterms:editor rdf:nodeID="abc"/> 8. </rdf:Description> Attribute to declare and refer a blank node 9. <rdf:Description rdf:nodeID="abc"> 10. <exterms:fullName>Dave Beckett</exterms:fullName> 11. <exterms:homePage rdf:resource="http://purl.org/net/dajobe/"/> 12. </rdf:Description> 13. </rdf:RDF> Linked Data & Semantic Web Technology
- 26. Anonymous Blank Nodes Attribute to declare Anonymous blank node 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:dc="http://purl.org/dc/elements/1.1/" 4. xmlns:exterms="http://example.org/stuff/1.0/"> 5. <rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar"> 6. <dc:title>RDF/XML Syntax Specification (Revised)</dc:title> 7. <exterms:editor rdf:parseType="Resource"> 8. <exterms:fullName>Dave Beckett</exterms:fullName> 9. <exterms:homePage rdf:resource="http://purl.org/net/dajobe/"/> 10. </exterms:editor> 11. </rdf:Description> 12. </rdf:RDF> 26 Linked Data & Semantic Web Technology
- 27. RDF/XML Using a Typed Literal ex:index.html exterms:creation-date "1999-08-16"^^xsd:date . Attribute to specify the datatype 1. <?xml version="1.0"?> 2. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 3. xmlns:exterms="http://www.example.org/terms/"> 4. <rdf:Description rdf:about="http://www.example.org/index.html"> 5. <exterms:creation-date rdf:datatype= "http://www.w3.org/2001/XMLSchema#date">1999-08-16 </exterms:creation-date> 6. </rdf:Description> 7. </rdf:RDF> 27 Linked Data & Semantic Web Technology
- 28. Defining Base URI • XML Base – facility for defining base URIs for parts of XML documents – to specify a base URI other than the base URI of the document or external entity 1. <?xml version="1.0"?> 2. <!DOCTYPE rdf:RDF [<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#">]> 3. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 4. xmlns:exterms="http://www.example.com/terms/" 5. xml:base="http://www.example.com/2002/04/products"> 6. <rdf:Description rdf:about="#item10245"> 7. <exterms:model rdf:datatype="&xsd;string">Overnighter</exterms:model> 8. <exterms:sleeps rdf:datatype="&xsd;integer">2</exterms:sleeps> 9. </rdf:Description> 10. </rdf:RDF> exterms:model “Overnighter”^^&xsd;string http://www.example.com/2002/04/products#item10245 exterms:sleeps 2^^&xsd;integer 28 Linked Data & Semantic Web Technology
- 29. rdf:ID Attribute • rdf:ID Attribute – to specify a fragment identifier, given by the value of the rdf:ID attribute – interpreted relative to a base URI appending the character "#" 1. <?xml version="1.0"?> 2. <!DOCTYPE rdf:RDF [<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#">]> 3. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 4. xmlns:exterms="http://www.example.com/terms/" 5. xml:base="http://www.example.com/2002/04/products"> 6. <rdf:Description rdf:ID="item10245"> 7. <exterms:model rdf:datatype="&xsd;string">Overnighter</exterms:model> 8. <exterms:sleeps rdf:datatype="&xsd;integer">2</exterms:sleeps> 9. </rdf:Description> 10. </rdf:RDF> exterms:model “Overnighter”^^&xsd;string http://www.example.com/2002/04/products#item10245 exterms:sleeps 2^^&xsd;integer 29 Linked Data & Semantic Web Technology
- 30. rdf:ID and rdf:about • The two forms are essentially synonyms: the full URIref formed by RDF/XML is the same in either case. • Using rdf:ID provides an additional check when assigning a set of distinct names. – A given value of the rdf:ID attribute can only appear once relative to the same base URI. 30 Linked Data & Semantic Web Technology
- 31. References • http://www.w3.org/TR/2004/REC-rdf-primer-20040210/ • http://en.wikipedia.org/wiki/Resource_description_framework • http://www.slideshare.net/lysander07/open-hpi-semweb02part2 • http://www.slideshare.net/lysander07/open-hpi-semweb02part3 • http://www.slideshare.net/lysander07/openhpi-24 • http://en.wikipedia.org/wiki/Qname • http://en.wikipedia.org/wiki/XML_Base 31 Linked Data & Semantic Web Technology