Semantic Web Introduction

2 Introduction Data Access Protocol SPARQL 1.1 Protocol SPARQL 1.1 Graph Store HTTP Protocol: Linked Data Platform Populating Web of Data RDFa GRDDL R2RML: mappings relational databases to RDF

3 SPARQL 1.1 Protocol Conveying SPARQL queries and updates to a processing service Returning the results via HTTP

4 SPARQL 1.1 Protocol Conveying SPARQL queries and updates to a processing service Returning the results via HTTP distinct * where { ?p ?v } limit 100

5 SPARQL 1.1 Protocol Conveying SPARQL queries and updates to a processing service Returning the results via HTTP distinct * where { ?p ?v } limit 100

6 SPARQL 1.1 Protocol Conveying SPARQL queries and updates to a processing service Returning the results via HTTP distinct * where { ?p ?v } limit 100

7 SPARQL 1.1 Protocol Conveying SPARQL queries and updates to a processing service Returning the results via HTTP data { }

8 SPARQL 1.1 Protocol Conveying SPARQL queries and updates to a processing service Returning the results via HTTP data { }

9 SPARQL 1.1 Graph Store HTTP Protocol Specifies the semantics of HTTP operations for managing a Graph Store. Directly interact with a graph store using HTTP Provides operations for: retrieving RDF graph content removing, creating, and replacing RDF graph content adding RDF statements to existing RDF graph content. HTTP GET:

10 SPARQL 1.1 Graph Store HTTP Protocol Specifies the semantics of HTTP operations for managing a Graph Store. Directly interact with a graph store using HTTP Provides operations for: retrieving RDF graph content removing, creating, and replacing RDF graph content adding RDF statements to existing RDF graph content. HTTP GET:

11 SPARQL 1.1 Graph Store HTTP Protocol Specifies the semantics of HTTP operations for managing a Graph Store. Directly interact with a graph store using HTTP Provides operations for: retrieving RDF graph content removing, creating, and replacing RDF graph content adding RDF statements to existing RDF graph content. HTTP GET:

12 SPARQL 1.1 Graph Store HTTP Protocol HTTP PUT: DROP + INSERT PUT /rdf-graph-store?graph=http%3A//server.example.org/test HTTP/1.1 Host: example.com Content-Type: ex: ex:Catherine a ex:Teacher. ex:Olivier a ex:Teacher.

13 SPARQL 1.1 Graph Store HTTP Protocol HTTP PUT: DROP + INSERT PUT /rdf-graph-store?graph=http%3A//server.example.org/test HTTP/1.1 Host: example.com Content-Type: ex: ex:Catherine a ex:Teacher. ex:Olivier a ex:Teacher.

14 SPARQL 1.1 Graph Store HTTP Protocol HTTP PUT: DROP + INSERT PUT /rdf-graph-store?graph=http%3A//server.example.org/test HTTP/1.1 Host: example.com Content-Type: ex: ex:Catherine a ex:Teacher. ex:Olivier a ex:Teacher.

15 SPARQL 1.1 Graph Store HTTP Protocol HTTP POST: INSERT HTTP DELETE

16 Linked Data 1. Use URIs as names for things 2. Use HTTP URIs so that people can look up those names 3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL) 4. Include links to other URIs, so that they can discover more things

17 Linked Data Platform Best practices for: read-write Linked Data architecture, based on HTTP access to web resources resources describe their state using RDF Clarifies the 4 rules of Linked Data: URI, HTTP URI, RDF/SPARQL, Link URI Discuss standard HTTP and RDF techniques and best practices for client/server that read and write Linked Data Container for partitioning space of resources Proposal of pagination for large graphs

18 Linked Data Platform LDPR servers MUST at least be HTTP/1.1 conformant servers [HTTP11] LDPR servers MUST provide an RDF representation for LDPRs. The HTTP Request-URI of the LDPR is typically the subject of most triples in the response LDPRs SHOULD reuse existing vocabularies instead of creating their own duplicate vocabulary terms. In addition to this general rule, some specific cases are covered by other conformance rules LDPR predicates SHOULD use standard vocabularies such as Dublin Core [DC-TERMS], RDF [RDF-CONCEPTS] and RDF Schema [RDF-SCHEMA], whenever possible LDPR representations SHOULD have at least one rdf:type set explicitly. This makes the representations much more useful to client applications that don’t support inferencing LDPR servers MAY support standard representations beyond those necessary to conform to this specification. These could be other RDF formats, like N3 or NTriples, but non-RDF formats like HTML [HTML401] and JSON [RFC4627] would likely be common.

19 RDF in Attributes: RDFa Add structured data to HTML pages directly Mark up human-readable Web page to express machine-readable data Semantic Web Date: Outstanding introduction to the Semantic Web (of Data) Ecole Polytechnique

20 RDF in Attributes: RDFa prefix ex: rdf:type ex:Course ; ex:date " " ; ex:location.

21 GRDDL Gleaning Resource Descriptions from Dialects of Languages Obtaining RDF data from XML documents Use a profile Indicate a transformation

22 GRDDL Use a profile Robin's Schedule...

23 GRDDL Indicate a transformation (e.g. XSLT) Robin's Schedule...

24 R2RML RDB to RDF Mapping Language 1. Direct Mapping of Relational Data to RDF 2. Customized Mapping from relational databases to RDF

25 R2RML Direct Mapping Direct translation of table to triples Subject is « Table/ID »Property is « Table#column » Type is « Table » Object is value of column rdf:type. "Catherine".. rdf:type. "Olivier".. Table: People IDfnameaddr (Address) 7Catherine18 8Olivier22 ………

26 R2RML Customized Mapping rr:logicalTable [ rr:tableName "EMP" ]; rr:subjectMap [ rr:template " rr:class ex:Teacher; ]; rr:predicateObjectMap [ rr:predicate foaf:name; rr:objectMap [ rr:column "ENAME" ]; ]. rdf:type ex:Teacher. foaf:name "Catherine". rdf:type ex:Teacher. foaf:name "Olivier".