[GitHub] [jena-site] afs opened a new pull request #11: 3.15.0: RDF* pages ; download version

[GitBox <gi...@apache.org>]

afs opened a new pull request #11:
URL: https://github.com/apache/jena-site/pull/11


   


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[GitHub] [jena-site] afs merged pull request #11: 3.15.0: RDF* pages ; download version

[GitBox <gi...@apache.org>]

afs merged pull request #11:
URL: https://github.com/apache/jena-site/pull/11


   


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[GitHub] [jena-site] kinow commented on a change in pull request #11: 3.15.0: RDF* pages ; download version

[GitBox <gi...@apache.org>]

kinow commented on a change in pull request #11:
URL: https://github.com/apache/jena-site/pull/11#discussion_r426916031



##########
File path: 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.

Review comment:
       s/They are occur/They occur/?




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