Package com.saxonica.ee.trans

Class PatternOptimizer

java.lang.Object

com.saxonica.ee.trans.PatternOptimizer

Direct Known Subclasses:

AncestorPatternOptimizer, ContainsTokenPatternOptimizer, EqualityPatternOptimizer, GeneralPatternOptimizer, IntEqualityPatternOptimizer

public abstract class PatternOptimizer
extends Object

A PatternOptimizer is an agent responsible for optimizing a particular class of patterns. It has two parts: a meta-pattern which determines which kinds of pattern it recognizes, and an action part which extracts characteristics and preconditions whose evaluation can be shared by all the rules in a rule chain

Constructor Summary

Constructors

Constructor	Description
PatternOptimizer()

Method Summary

Modifier and Type	Method	Description
protected void	addPrecondition(RuleEE rule, Map<Precondition,List<RuleEE>> preconditions, Precondition p)
protected Characteristic	allocateCharacteristic(Map<Characteristic,Characteristic> characteristics, Characteristic newChic)	Allocate a new characteristic, that is, a property of nodes or other items that may potentially be used in evaluating the preconditions of more than one pattern.
abstract boolean	appliesTo(Pattern pattern)	Ask whether this pattern optimizer is applicable to a particular pattern
abstract void	process(RuleEE rule, Pattern pattern, Map<Precondition,List<RuleEE>> preconditions, Map<Characteristic,Characteristic> characteristics)	Process a particular pattern, potentially adding to the list of preconditions and characteristics maintained when processing a set of rules

Methods inherited from class java.lang.Object

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

Constructor Details

PatternOptimizer

public PatternOptimizer()

Method Details

appliesTo

public abstract boolean appliesTo(Pattern pattern)

Ask whether this pattern optimizer is applicable to a particular pattern

Parameters:

pattern - the pattern in question

Returns:

true if this pattern optimizer is applicable to this pattern

process

public abstract void process(RuleEE rule,
 Pattern pattern,
 Map<Precondition,List<RuleEE>> preconditions,
 Map<Characteristic,Characteristic> characteristics)

Process a particular pattern, potentially adding to the list of preconditions and characteristics maintained when processing a set of rules

Parameters:

rule - the rule to be processed

pattern - the pattern used by this rule

preconditions - a collection of preconditions maintained for a set of rules

characteristics - a collection of characteristics maintained for a set of rules. This is maintained as a map from characteristics to characteristics in which the key and the value are always the same; the reason for this curious structure is that when an equivalent characteristic is already present in the map, we want to return the existing characteristic to replace the new one; a Java Set does not have any (efficient) operation to "find the existing value in the set that is equal to X".

allocateCharacteristic

protected Characteristic allocateCharacteristic(Map<Characteristic,Characteristic> characteristics,
 Characteristic newChic)

Allocate a new characteristic, that is, a property of nodes or other items that may potentially be used in evaluating the preconditions of more than one pattern.

Parameters:

characteristics - The set of characteristics to be added to. This maintained as a map from characteristics to characteristics for reasons explained at process(RuleEE, Pattern, Map, Map).

newChic - a new characteristic to be added to the set.

Returns:

the supplied characteristic unless there was already an equivalent characteristic in the set, in which case an equivalent characteristic that should be used in place of the new one.

addPrecondition

protected void addPrecondition(RuleEE rule,
 Map<Precondition,List<RuleEE>> preconditions,
 Precondition p)