com.bigdata.rdf.sparql.ast.VarNode Maven / Gradle / Ivy
package com.bigdata.rdf.sparql.ast;
import java.util.Map;
import com.bigdata.bop.BOp;
import com.bigdata.bop.IValueExpression;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.Var;
import com.bigdata.rdf.internal.IV;
/**
* Used to represent a variable in the AST.
*
* Note: Unlike {@link Var}, this class does NOT support reference testing for
* equality. Multiple {@link VarNode} instances MAY exist for the same
* {@link IVariable}. You must either compare the value returned by
* {@link #getVar()} (which is canonical) or use {@link #equals(Object)}.
*
* @author mikepersonick
*/
public class VarNode extends TermNode {
/**
*
*/
private static final long serialVersionUID = 2368082533964951789L;
public interface Annotations extends TermNode.Annotations {
/**
* Annotation marks anonymous variables (a variable created by the
* interpretation of the parse tree, AST, etc rather than one given
* directly in the original query).
*/
String ANONYMOUS = "anon";
boolean DEFAULT_ANONYMOUS = false;
/*
* Note: Annotating variables which are "SIDS" does not work out because
* we lack sufficient context in the parser to make this determination
* when the variable appears outside of the BIND( <<...>> as ?sid )
* context. In order for the parser to do this it would have to reason
* about the visibility of variables as well, which is just too much
* effort.
*/
// /**
// * Annotation marks a variable which is a statement identifier.
// *
// * @see
// * Reification Done Right
// */
// String SID = "sid";
//
// boolean DEFAULT_SID = false;
/**
* Annotation marks a variable which is actually the name of a solution
* set.
*/
String SOLUTION_SET = "solutionSet";
boolean DEFAULT_SOLUTION_SET = false;
}
/**
* Constructor required for {@link com.bigdata.bop.BOpUtility#deepCopy(FilterNode)}.
*/
public VarNode(VarNode op) {
super(op);
}
/**
* Required shallow copy constructor.
*/
public VarNode(final BOp[] args, final Map anns) {
super(args, anns);
}
@SuppressWarnings("unchecked")
public VarNode(final String var) {
this(Var.var(var));
}
@SuppressWarnings("rawtypes")
public VarNode(final IVariable var) {
super(new BOp[]{var}, null);
// setValueExpression(var);
}
/**
* Return true if this is an anonymous variable (anonymous
* variables are introduced during a rewrite of the query in which blank
* nodes are replaced by anonymous variables). This marker is useful mainly
* when reading the AST tree as an aid to understanding where a given
* variable came from in the original query.
*/
public boolean isAnonymous() {
return getProperty(Annotations.ANONYMOUS, Annotations.DEFAULT_ANONYMOUS);
}
/**
* Mark this as an anonymous variable (one introduced during a query rewrite
* in place of a blank node).
*
* @param anonymous
*/
public void setAnonymous(final boolean anonymous) {
setProperty(Annotations.ANONYMOUS, anonymous);
((Var) getValueExpression()).setAnonymous(anonymous);
}
// /**
// * Return true if this is an SID variable (a variable which
// * binds statement identifiers composed from triples). This marker is useful
// * mainly when reading the AST tree as an aid to understanding where a given
// * variable came from in the original query.
// */
// public boolean isSID() {
//
// return getProperty(Annotations.SID, Annotations.DEFAULT_SID);
//
// }
//
// /**
// * Mark this as an SID variable (one which represents a triple reference
// * pattern).
// *
// * @param val
// */
// public void setSID(final boolean val) {
//
// setProperty(Annotations.SID, val);
//
// }
/**
* Return true if the variable represents a solution set name.
*/
public boolean isSolutionSet() {
return getProperty(Annotations.SOLUTION_SET,
Annotations.DEFAULT_SOLUTION_SET);
}
/**
* Mark this as a variable which actually conveys the name of a solution
* set.
*
* @param true if the variable represents a solution set name.
*/
public void setSolutionSet(final boolean solutionSet) {
setProperty(Annotations.SOLUTION_SET, solutionSet);
}
/**
* Return true iff the variable is *.
*/
public boolean isWildcard() {
return getValueExpression().isWildcard();
}
/**
* Strengthen return type.
*/
@SuppressWarnings("rawtypes")
@Override
public IVariable getValueExpression() {
return (IVariable) super.getValueExpression();
}
/**
* Hot-swap the IVariable underneath this VarNode.
*/
@Override
public void setValueExpression(IValueExpression ve) {
setArg(0, ve);
}
/**
* Overridden to mark metadata about variables.
*/
@Override
public String toString() {
return "VarNode(" + getValueExpression() + ")"
+ (isAnonymous() ? "[anonymous]" : "")
// + (isSID() ? "[sid]" : "")
+ (isSolutionSet() ? "[solutionSet]" : "")
;
}
/**
* @return a varnode containing a fresh (uniquely distinct) variable
*/
public static VarNode freshVarNode() {
return new VarNode((Var)Var.var());
}
}