This is an automated email from the ASF dual-hosted git repository. andy pushed a commit to branch rdfstar in repository https://gitbox.apache.org/repos/asf/jena-site.git
commit 120dd96b8ac88ca2db595d62bd0706221b8f4d1b Author: Andy Seaborne <[email protected]> AuthorDate: Mon May 18 21:50:48 2020 +0100 Documentation for RDF* --- .gitignore | 2 + layouts/_default/baseof.html | 4 +- source/documentation/rdfstar/__index.md | 118 ++++++++++++++++++++++++++++++++ 3 files changed, 122 insertions(+), 2 deletions(-) diff --git a/.gitignore b/.gitignore index c1a3c44..374f427 100644 --- a/.gitignore +++ b/.gitignore @@ -2,6 +2,8 @@ /resources target +.vscode + # IntelliJ generated *.iml .idea diff --git a/layouts/_default/baseof.html b/layouts/_default/baseof.html index ab63f73..11666c4 100644 --- a/layouts/_default/baseof.html +++ b/layouts/_default/baseof.html @@ -72,17 +72,17 @@ <li><a href="/documentation/javadoc.html">Javadoc</a></li> <li><a href="/documentation/rdf/index.html">RDF API</a></li> <li><a href="/documentation/io/">RDF I/O</a></li> + <li><a href="/documentation/fuseki2/index.html">Fuseki</a></li> <li><a href="/documentation/query/index.html">ARQ (SPARQL)</a></li> <li><a href="/documentation/rdfconnection/">RDF Connection - SPARQL API</a></li> <li><a href="/documentation/tdb/index.html">TDB</a></li> <li><a href="/documentation/tdb2/index.html">TDB2</a></li> <li><a href="/documentation/query/text-query.html">Text Search</a></li> <li><a href="/documentation/shacl/index.html">SHACL</a></li> - <li><a href="/documentation/geosparql/index.html">GeoSPARQL</a></li> + <li><a href="/documentation/rdfstar/index.html">RDF*</a></li> <li><a href="/documentation/tools/index.html">Command-line tools</a></li> <li><a href="/documentation/hadoop/index.html">Elephas - tools for RDF on Hadoop</a></li> <li><a href="/documentation/jdbc/index.html">SPARQL over JDBC</a></li> - <li><a href="/documentation/fuseki2/index.html">Fuseki</a></li> <li><a href="/documentation/permissions/index.html">Permissions</a></li> <li><a href="/documentation/assembler/index.html">Assembler</a></li> <li><a href="/documentation/ontology/">Ontology API</a></li> diff --git a/source/documentation/rdfstar/__index.md b/source/documentation/rdfstar/__index.md new file mode 100644 index 0000000..1360a26 --- /dev/null +++ b/source/documentation/rdfstar/__index.md @@ -0,0 +1,118 @@ +--- +title: Support of RDF* +slug: index +--- +[RDF\*](https://arxiv.org/abs/1406.3399) is an extension to RDF that provides +a way for one triple to refer to another triple. Another resource about RDF\* is +[Olaf Hartig's blog entry](https://blog.liu.se/olafhartig/2019/01/10/position-statement-rdf-star-and-sparql-star/). + +Example: + +```turtle +<< :john foaf:name "John Smith" >> dct:source <http://example/directory> . +``` + +The part `<< :john foaf:name "John Smith" >>` is a triple term and refers to the triple with subject `:john`, property `foaf:name` and object `"John Smith"`. + +Triple terms can be in the subject or object position. + +Jena provides support for RDF\* and the related SPARQL\*. + +Support for RDF* is experimentation in Jena 3.15.0 (released May 2020): + +* Turtle, N-Triples, TriG and N-Quads extended for Triple Terms syntax. There is no output in RDF/XML. +* SPARQL extended with Triple Term syntax for graph matching (in code, use `Syntax.syntaxARQ`). +* SPARQL Result formats for JSON and XML extended to support Triple Terms in results. +* Support in memory-based storage (graphs and datasets). +* Support in the Model API. + +All this is active by default in Fuseki. + +This support is experimental and subject to change. The aim is to follow the definition of RDF* as well as emerging _de facto_ consensus in other implementations. + +Later releases will extend support to persistent storage in [TDB1](/documentation/tdb) and [TDB2](/documentation/tdb2/). + +## RDF\* + +RDF\* syntax for triple terms is added to the parsers for Turtle, N-Triples, TriG and N-Quads. + +Datasets may have graphs that have triple terms that refer to triples anywhere, not just in the same graph. + +## SPARQL\* + +Matches for triple terms: + +```sparql +SELECT ?name { <<:john foaf:name ?name >> dct:source <http://example/directory> } +``` + +Insert triples terms into the default graph to record the graph source. + +```sparql +INSERT { <<?s ?p ?o>> dct:source <http://example/directory> } +WHERE { + GRAPH <http://example/directory> { + ?s ?p ?o + } +} +``` + +### SPARQL Functions related to triple terms + +These functions cause an expression error if passed the wrong type of arguments. `afn:` +is a prefix for `<http://jena.apache.org/ARQ/function#>`. + +| Function | Description | +| -------- | ----------- | +| `afn:subject(?t)` | Return the subject of the triple term | +| `afn:predicate(?t)` | Return the predicate (property) of the triple term | +| `afn:object(?t)` | Return the object of the triple term | +| `afn:triple(?s, ?p, ?o)` | Create a triple term from s/p/o | +| `afn:isTriple(?t)` | Return true if the argument value is a triple term | + +### SPARQL results + +The syntaxes for SPARQL results from a SELECT query, `application/sparql-results+json`, +`application/sparql-results+xml` are extended to include triple terms: + +The triple term `<< _:b0 <http://example/p> 123 >>` is encoded, in +`application/sparql-results+json` as: + +```json + { + "type": "triple" , + "value": { + "subject": { "type": "bnode" , "value": "b0" } , + "property": { "type": "uri" , "value": "http://example/p"; } , + "object": { "type": "literal" , "datatype": "http://www.w3.org/2001/XMLSchema#integer"; , "value": "123" } + } +``` + +and similarly in `application/sparql-results+xml`: + +```xml + <triple> + <subject> + <bnode>b0</bnode> + </subject> + <property> + <uri>http://example/p</uri> + </property> + <object> + <literal datatype="http://www.w3.org/2001/XMLSchema#integer";>123</literal> + </object> + </triple> +``` + +## Model API + +RDF* triple terms are treated as `Resource` to preserve the typed Model API. +They are occur in the subject and object positions. + +A `Resource` contains a `Statement` object if the underlying RDF term is a RDF* triple term. + +New methods include: + +* `Statement Resource.getStatement()` +* `Resource Model.createResource(Statement)` +* `Resource ResourceFactory.createStatement`
