uk.ac.starlink.table.join

Class HumanMatchEngine

java.lang.Object

uk.ac.starlink.table.join.HumanMatchEngine

All Implemented Interfaces:

MatchEngine

public class HumanMatchEngine
extends Object
implements MatchEngine

MatchEngine adaptor which transforms the base engine so that it uses more human-friendly units. Currently, this means that it eschews radians in favour of degrees or arcseconds for angular quantities; it decides which on the basis of UCDs. In other respects, this engine will behave exactly the same as its base engine. If the base engine has no human-unfriendly units, this one should behave exactly the same.

Since:

2 Sep 2005

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
HumanMatchEngine(MatchEngine baseEngine) Constructor.

Method Summary

Modifier and Type	Method and Description
java.util.function.Supplier<Coverage>	createCoverageFactory() Returns a supplier for coverage objects.
java.util.function.Supplier<MatchKit>	createMatchKitFactory() Returns a factory for MatchKit instances corresponding to the current settings of this object.
static MatchEngine	getHumanMatchEngine(MatchEngine base) Returns a human-friendly version of a supplied MatchEngine.
DescribedValue[]	getMatchParameters() Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria.
ValueInfo	getMatchScoreInfo() Returns a description of the value returned by the MatchKit.matchScore(java.lang.Object[], java.lang.Object[]) method.
double	getScoreScale() Returns a scale value for the match score.
DescribedValue[]	getTuningParameters() Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match.
ValueInfo[]	getTupleInfos() Returns a set of ValueInfo objects indicating what is required for the elements of each tuple.
boolean	isIdentity() Indicates whether this object simply duplicates the underlying MatchEngine.
boolean	isLargeAngle(ValueInfo info) Indicates whether a given value is recognised as representing a large angle (such as a coordinate of some kind).
boolean	isSmallAngle(ValueInfo info) Indicates whether a given value is recognised as representing a small angle (such as an error of some kind).

Methods inherited from class java.lang.Object

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

Constructor Detail

HumanMatchEngine

public HumanMatchEngine(MatchEngine baseEngine)

Constructor.

Parameters:

baseEngine - the match engine supplying the base behaviour for this one

Method Detail

isIdentity

public boolean isIdentity()

Indicates whether this object simply duplicates the underlying MatchEngine.

Returns:

true if this wrapper makes no changes to underlying behaviour, false if it may make changes

getMatchParameters

public DescribedValue[] getMatchParameters()

Description copied from interface: MatchEngine

Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria. Typically at least one of these will be some sort of tolerance separation which determines how close tuples must be to count as a match. This match engine's behaviour can be modified by calling DescribedValue.setValue(java.lang.Object) on the returned objects.

Specified by:

getMatchParameters in interface MatchEngine

Returns:

array of described values which influence the match

getTuningParameters

public DescribedValue[] getTuningParameters()

Description copied from interface: MatchEngine

Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match. This match engine's performance can be influenced by calling DescribedValue.setValue(java.lang.Object) on the returned objects.

Changing these values will make no difference to the output of MatchKit.matchScore(java.lang.Object[], java.lang.Object[]), but may change the output of MatchKit.getBins(java.lang.Object[]). This may change the CPU and memory requirements of the match, but will not change the result. The default value should be something sensible, so that setting the value of these parameters is not in general required.

Specified by:

getTuningParameters in interface MatchEngine

Returns:

array of described values which may influence match performance

getTupleInfos

public ValueInfo[] getTupleInfos()

Description copied from interface: MatchEngine

Returns a set of ValueInfo objects indicating what is required for the elements of each tuple. The length of this array is the number of elements in the tuple. Each element should at least have a defined name and content class. The info's nullable attribute has a special meaning: if true it means that it makes sense for this element of the tuple to be always blank (for instance assigned to no column).

Specified by:

getTupleInfos in interface MatchEngine

Returns:

array of objects describing the requirements on each element of the tuples used for matching

createMatchKitFactory

public java.util.function.Supplier<MatchKit> createMatchKitFactory()

Description copied from interface: MatchEngine

Returns a factory for MatchKit instances corresponding to the current settings of this object.

The returned value is immutable, and is not affected by subsequent changes of the settings of this object.

Specified by:

createMatchKitFactory in interface MatchEngine

Returns:

match kit supplier

createCoverageFactory

public java.util.function.Supplier<Coverage> createCoverageFactory()

Description copied from interface: MatchEngine

Returns a supplier for coverage objects. Each such coverage can be used to characterise a region of tuple space. When populated with a set of tuples A, any tuple for which the inclusion function defined by its Coverage.createTestFactory() method returns false is guaranteed not to match any tuple in A according to this object's match criteria.

The returned value is immutable, and is not affected by subsequent changes of the settings of this object.

If no suitable implementation is available, null may be returned.

Specified by:

createCoverageFactory in interface MatchEngine

Returns:

supplier of coverage objects, or null

getScoreScale

public double getScoreScale()

Description copied from interface: MatchEngine

Returns a scale value for the match score. The intention is that the result of matchScore/MatchEngine.getScoreScale() is of order unity, and is thus comparable between different match engines.

As a general rule, the result should be the maximum value ever returned from the matchScore method, corresponding to the least good successful match. For binary MatchEngine implementations (all matches are either score=0 or failures) a value of 1 is recommended. If nothing reliable can be said about the scale, NaN may be returned.

Specified by:

getScoreScale in interface MatchEngine

Returns:

scale of successful match scores, a positive finite number or NaN

getMatchScoreInfo

public ValueInfo getMatchScoreInfo()

Description copied from interface: MatchEngine

Returns a description of the value returned by the MatchKit.matchScore(java.lang.Object[], java.lang.Object[]) method. The content class should be numeric (though need not be Double), and the name, description and units should be descriptive of whatever the physical significance of the value is. If the result of matchScore is not interesting (for instance, if it's always either 0 or -1), null may be returned.

Specified by:

getMatchScoreInfo in interface MatchEngine

Returns:

metadata for the match score results

isLargeAngle

public boolean isLargeAngle(ValueInfo info)

Indicates whether a given value is recognised as representing a large angle (such as a coordinate of some kind).

Parameters:

info - value metadata

Returns:

true if info is known to represent a large angle

isSmallAngle

public boolean isSmallAngle(ValueInfo info)

Indicates whether a given value is recognised as representing a small angle (such as an error of some kind).

Parameters:

info - value metadata

Returns:

true if info is known to represent a small angle

getHumanMatchEngine

public static MatchEngine getHumanMatchEngine(MatchEngine base)

Returns a human-friendly version of a supplied MatchEngine. If no changes are required, the original instance is returned.

Parameters:

base - original match engine

Returns:

human-friendly version