/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/* Portions of this code are:
*
* Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2007.
*
* Licensed under the Aduna BSD-style license.
*/
/*
* Created on Aug 21, 2011
*/
package com.bigdata.rdf.sail.sparql;
import java.util.Map;
import org.openrdf.model.Value;
import org.openrdf.model.vocabulary.RDF;
import com.bigdata.rdf.model.BigdataValue;
import com.bigdata.rdf.model.BigdataValueFactory;
import com.bigdata.rdf.model.BigdataValueFactoryImpl;
import com.bigdata.rdf.sail.sparql.ast.VisitorException;
import com.bigdata.rdf.sparql.ast.ConstantNode;
import com.bigdata.rdf.sparql.ast.VarNode;
/**
* Object provides context required in various stages of parsing queries or
* updates.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @openrdf
*/
public class BigdataASTContext {
protected final BigdataValueFactory valueFactory;
/**
* A mapping of parsed RDF Values and well known vocabulary items used when
* generating the AST to resolved {@link BigdataValue}s. This includes
* everything which was parsed plus certain well-known items such as
* {@link RDF#FIRST}, {@link RDF#REST}, and {@link RDF#NIL} which are only
* used when handling syntactic sugar constructions.
*/
protected final Map<Value,BigdataValue> vocab;
/**
* Counter used to generate unique (within query) variable names.
*/
private int constantVarID = 1;
/**
*
* @param values
* A map from the distinct RDF {@link Value} objects in the QUERY
* or UPDATE request to the corresponding {@link BigdataValue}
* objects that will be used to process the request.
*/
public BigdataASTContext(final Map<Value, BigdataValue> values) {
this.valueFactory = BigdataValueFactoryImpl.getInstance("");
this.vocab = values;
}
/**
* Create an anonymous variable. The variable name will be unique (within
* the scope of the query parser) and {@link VarNode#isAnonymous()} will
* return <code>true</code>.
*
* @param varName
* The prefix of the name of an anonymous variable. This should
* have the pattern <code>-foo-</code>. An unique (within query)
* variable identifier will be appended to the prefix.
*
* @return The anonymous variable.
*/
protected VarNode createAnonVar(final String varName) {
final VarNode var = new VarNode(varName + constantVarID++);
var.setAnonymous(true);
return var;
}
/**
* Return a constant for a pre-defined vocabulary item.
*
* @throws VisitorException
*/
protected ConstantNode createConstVar(final Value value)
throws VisitorException {
final BigdataValue v = vocab.get(value);
if (v == null)
throw new VisitorException("Undefined vocabulary: " + value);
return new ConstantNode(v.getIV());
}
/**
* Return a new variable for a SID (Statement Identifier)
*
* @see <a href="https://sourceforge.net/apps/trac/bigdata/ticket/526">
* Reification Done Right</a>
*/
protected VarNode createSidVar() {
final VarNode var = new VarNode("-sid-" + constantVarID++);
return var;
}
}