Package edu.harvard.seas.pl.abcdatalog.engine.topdown

Class AbstractQsqEngine

java.lang.Object

edu.harvard.seas.pl.abcdatalog.engine.topdown.AbstractQsqEngine

All Implemented Interfaces:

DatalogEngine

Direct Known Subclasses:

IterativeQsqEngine, RecursiveQsqEngine

public abstract class AbstractQsqEngine
extends Object
implements DatalogEngine

A Datalog engine that uses a variant of the query-subquery evaluation method.

Field Summary

Fields

Modifier and Type	Field	Description
protected final Map<PredicateSym,Relation>	edbRelations	EDB facts mapped by predicate symbol.
protected final Map<PredicateSym,Set<DatalogValidator.ValidClause>>	idbRules	Rules for deriving IDB facts mapped by predicate symbol.

Constructor Summary

Constructors

Constructor	Description
AbstractQsqEngine()

Method Summary

Modifier and Type	Method	Description
protected Tuple	applyBoundArgs(Tuple t, List<Boolean> adornment, Tuple input)	Creates a new tuple that is like t except the bound terms of t have been replaced by the terms in input.
protected Set<PositiveAtom>	checkIfEdbQuery(PositiveAtom q)	If query is for an EDB relation, returns facts that unify with that query.
void	init(Set<Clause> program)	Initializes engine with a Datalog program, including EDB facts.
abstract Set<PositiveAtom>	query(PositiveAtom q)	Returns all facts that 1) can be derived from the rules and initial facts that were used to initialize this engine and 2) unify with the query.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface edu.harvard.seas.pl.abcdatalog.engine.DatalogEngine

query

Field Details

edbRelations

protected final Map<PredicateSym,Relation> edbRelations

EDB facts mapped by predicate symbol.

idbRules

protected final Map<PredicateSym,Set<DatalogValidator.ValidClause>> idbRules

Rules for deriving IDB facts mapped by predicate symbol.

Constructor Details

AbstractQsqEngine

public AbstractQsqEngine()

Method Details

init

public void init(Set<Clause> program)
          throws DatalogValidationException

Description copied from interface: DatalogEngine

Initializes engine with a Datalog program, including EDB facts. The set that is passed into this method should include rules for deriving new facts as well as the initial facts, which can be encoded as clauses with empty bodies.

Specified by:

init in interface DatalogEngine

Parameters:

program - program to evaluate

Throws:

DatalogValidationException

DatalogValidationException - if the given program is invalid

query

public abstract Set<PositiveAtom> query(PositiveAtom q)

Description copied from interface: DatalogEngine

Returns all facts that 1) can be derived from the rules and initial facts that were used to initialize this engine and 2) unify with the query.

Specified by:

query in interface DatalogEngine

Parameters:

q - the query

Returns:

facts

applyBoundArgs

protected Tuple applyBoundArgs(Tuple t,
 List<Boolean> adornment,
 Tuple input)

Creates a new tuple that is like t except the bound terms of t have been replaced by the terms in input.

Parameters:

t -

adornment - specifies bound terms of t

input -

Returns:

new tuple

checkIfEdbQuery

protected Set<PositiveAtom> checkIfEdbQuery(PositiveAtom q)

If query is for an EDB relation, returns facts that unify with that query.

Parameters:

q - query

Returns:

facts, or null if query is for an IDB relation