/**
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
*/
/*
* Created on June 12, 2015
*/
package com.bigdata.rdf.sparql.ast;
import java.util.Set;
import com.bigdata.bop.IVariable;
/**
* Interface describing constraints and desiderata w.r.t. variable bindings
* that should, must, or must not be present at the time when executing the
* construct.
*
* @author <a href="mailto:ms@metaphacts.com">Michael Schmidt</a>
* @version $Id$
*/
public interface IVariableBindingRequirements {
/**
* Return the variables used in the node that *must* be bound prior to
* evaluating the node. For instance, when evaluation a SPARQL 1.1
* service and the endpoint is specified through a variable, then this
* variable must be bound in order to identify the endpoint to which the
* query is to be sent.
*
* By *must* be bound we mean that, if it is possible to bring the variables
* in a join group in order such that they are bound when executing the
* construct (e.g., think of a FILTER), then we *must* consider that.
* However, when the {@link IVariableBindingRequirements#getRequiredBound()}
* interface cannot be satisified, the query may still be valid and return
* results (for the SPARQL 1.1 service example mentioned above, it may not,
* for the FILTER it may).
*
* The set of these variables must be disjoint from
* {@link IVariableBindingRequirements#getRequiredUnound()}.
*
* @return the set of variables that must be bound prior to evaluation
*/
public Set<IVariable<?>> getRequiredBound(final StaticAnalysis sa);
/**
* Get variables that are not required to be bound, but desired in the
* sense that we want them to be bound when evaluating the construct.
* In general, the more variables are bound, the better, but this might
* differ for certain constructs. Should only report variables that are
* *not* reported through method
* {@link IVariableBindingRequirements#getRequiredBound(StaticAnalysis)}.
*
* @return the set of variables that are desires to be bound, but not
* required
*/
public Set<IVariable<?>> getDesiredBound(final StaticAnalysis sa);
}