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From jpz6311...@apache.org
Subject svn commit: r1696184 - /jena/site/trunk/content/documentation/query/construct-quad.mdtext
Date Sun, 16 Aug 2015 23:36:58 GMT
Author: jpz6311whu
Date: Sun Aug 16 23:36:58 2015
New Revision: 1696184

URL: http://svn.apache.org/r1696184
Log:
compose doc for construct-quad.mdtext

Modified:
    jena/site/trunk/content/documentation/query/construct-quad.mdtext

Modified: jena/site/trunk/content/documentation/query/construct-quad.mdtext
URL: http://svn.apache.org/viewvc/jena/site/trunk/content/documentation/query/construct-quad.mdtext?rev=1696184&r1=1696183&r2=1696184&view=diff
==============================================================================
--- jena/site/trunk/content/documentation/query/construct-quad.mdtext (original)
+++ jena/site/trunk/content/documentation/query/construct-quad.mdtext Sun Aug 16 23:36:58
2015
@@ -1,2 +1,97 @@
-Title: ARQ - Construct Quad
+# ARQ - Construct Quad
+
+## Introduction
+The current W3C recommendation of [SPARQL 1.1](http://www.w3.org/TR/sparql11-query/) supports
the CONSTRUCT query form, which returns a single RDF graph specified by a graph template.
+The result is an RDF graph formed by taking each query solution in the solution sequence,
substituting for the variables in the graph template, and combining the triples into a single
RDF graph by set union.
+However, it does not directly generate quads or [RDF datasets](http://www.w3.org/TR/sparql11-query/#rdfDataset).

+In order to eliminate this limitation, Jena ARQ extends the grammar of the CONSTRUCT query
form and provides the according components, which brings more conveniences for the users manipulating
RDF datasets with SPARQL.
+
+## Query Syntax
+
+A CONSTRUST template of the SPARQL 1.1 query String is [Turtle](http://www.w3.org/TR/turtle/)
format with possible variables.
+The syntax for this extension follows that style in ARQ, using [TriG](http://www.w3.org/TR/trig/)
plus variables. 
+Just like SPARQL 1.1, there're 2 forms for ARQ Contruct Quad query String:
+
+### Complete Form
+
+    CONSTRUCT {
+        # Named graph
+        GRAPH :g { ?s :p ?o }
+        # Default graph
+        { ?s :p ?o }
+        # Named graph
+        ?g { :s ?p :o }
+        # Default graph
+        :s ?p :o
+    } WHERE { 
+        # SPARQL 1.1 WHERE Clause
+	... 
+    }
+
+The default graphs and the named graphs can be constructed within the CONSTRUCT clause in
the above way.
+Note that, for constructing the named graph, the token of GRAPH can be optional.
+The brackets of the triples to be constructed in the default graph can also be optional.
+
+### Short Form
+
+    CONSTRUCT WHERE { 
+        # Basic dataset pattern (only the default graph and the named graphs)
+	... 
+    }
+
+A short form is provided for the case where the template and the pattern are the same and
the pattern is just a basic dataset pattern (no FILTERs and no complex graph patterns are
allowed in the short form). The keyword WHERE is required in the short form.
+
+### Grammar
+
+The normative definition of the syntax grammar of the query string is defined in this table:
+
+ConstructQuery            | ::= 'CONSTRUCT' ( ConstructTemplate DatasetClause* WhereClause
SolutionModifier | DatasetClause* 'WHERE'  '{' ConstructQuads '}' SolutionModifier )
+ConstructTemplate         | ::= '{' ConstructQuads '}¡¯
+ConstructQuads            | ::= TriplesTemplate? ( ConstructQuadsNotTriples '.'? TriplesTemplate?
)*
+ConstructQuadsNotTriples  | ::= ( 'GRAPH'  VarOrIri )?   '{' TriplesTemplate? '}'
+TriplesTemplate           | ::= TriplesSameSubject ( '.' TriplesTemplate? )?
+DatasetClause, WhereClause, SolutionModifier, TriplesTemplate, VarOrIri, TriplesSameSubject
| [SPARQL 1.1 Grammar](http://www.w3.org/TR/sparql11-query/#grammar)
+
+## Programming API
+
+ARQ provides 2 additional methods in QueryExecution for Construct Quad.
+
+    Iterator<Quad> QueryExecution.execConstructQuads() // allow duplication
+    Dataset QueryExecution.execConstructDataset() // no duplication
+
+One difference of the 2 methods is: 
+The method of execConstructQuads() returns an Iterator of Quad, allowing duplication.
+But execConstructDataset() constructs the desired Dataset object with only unique Quads.
+
+In order to use these methods, it's required to swtich on the query syntax of ARQ beforehead,
when creating the Query object:
+    
+    Query query = QueryFactory.create(queryString, Syntax.syntaxARQ);
+
+If the query is supposed to construct only triples, not quads, the triples will be constructed
in the default graph. For example:
+
+    String queryString = "CONSTRUCT { ?s ?p ?o } WHERE ... "
+    ...
+    Iterator<Quad> quads = qexec.execConstructQuads(); // The graph node of the quads
are the default graph (ARQ uses <urn:x-arq:DefaultGraphNode>).
+
+If the query string stands for constructing quads while the method of exeConstructTriples()
are called,
+it returns only the triples in the default graph of the CONSTRUCT query template. It's called
a "projection" on the default graph. For instance:
+
+    String queryString = "CONSTRUCT { ?s ?p ?o . GRAPH ?g1 { ?s1 ?p1 ?o1 } } WHERE ..."
+    ...
+    Iterator<Triple> triples = qexec.exeConstructTriples(); // The part of "GRAPH ?g1
{ ?s1 ?p1 ?o1 }" will be ignored. Only "?s ?p ?o" in the default graph will be returned.
+
+More examples can be found at jena-arq/src-examples/arq/examples/constructquads/ExampleConstructQuads.java
+
+## Fuseki Support
+
+Jena [Fuseki] is also empowed with Construct Quad query as a built-in function. No more addtional
configuration is required to switch it on.
+Because [QueryEngineHTTP](http://jena.apache.org/documentation/javadoc/arq/com/hp/hpl/jena/sparql/engine/http/QueryEngineHTTP.html)
is just an implementation of QueryExcecution, there's no much difference for the client users
to manipulate the programming API described in the previous sections, e.g.
+
+    String queryString = " CONSTRUCT { GRAPH <http://example/ns#g1> {?s ?p ?o} } WHERE
{?s ?p ?o}" ;
+    Query query = QueryFactory.create(queryString, Syntax.syntaxARQ);
+    try ( QueryExecution qExec = QueryExecutionFactory.sparqlService(serviceQuery, query)
) { // serviceQuery is the URL of the remote service
+        Iterator<Quad> result = qExec.execConstructQuads();
+	...
+    }
+    ...
 



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