Class EqualsMatchEngine
- All Implemented Interfaces:
MatchEngine
The equality is roughly in the sense of Object.equals(java.lang.Object)
,
but some additional work is done, so that for instance (multi-dimensional)
arrays are compared (recursively) on their contents, and blank objects
are compared in the sense used in the rest of STIL. A blank value is
not considered equal to anything, including another blank value.
Scalar numeric values are, as far as possible, compared on numeric
value rather than object equality, though this numeric value comparison
does not currently apply to arrays.
- Since:
- 25 Mar 2004
- Author:
- Mark Taylor (Starlink)
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionReturns null.Returns a factory for MatchKit instances corresponding to the current settings of this object.uk.ac.starlink.table.DescribedValue[]
Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria.uk.ac.starlink.table.ValueInfo
The match score is uninteresting, since it's either -1 or 0.double
Returns a scale value for the match score.uk.ac.starlink.table.DescribedValue[]
Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match.uk.ac.starlink.table.ValueInfo[]
Returns a set of ValueInfo objects indicating what is required for the elements of each tuple.toString()
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Constructor Details
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EqualsMatchEngine
public EqualsMatchEngine()
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Method Details
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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 interfaceMatchEngine
- Returns:
- match kit supplier
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createCoverageFactory
Returns null. You could check bounds on hashcodes, but it's not likely to be very revealing.- Specified by:
createCoverageFactory
in interfaceMatchEngine
- Returns:
- supplier of coverage objects, or null
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getScoreScale
public double getScoreScale()Description copied from interface:MatchEngine
Returns a scale value for the match score. The intention is that the result ofmatchScore
/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 interfaceMatchEngine
- Returns:
- scale of successful match scores, a positive finite number or NaN
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getMatchScoreInfo
public uk.ac.starlink.table.ValueInfo getMatchScoreInfo()The match score is uninteresting, since it's either -1 or 0. We flag this by returningnull
here.- Specified by:
getMatchScoreInfo
in interfaceMatchEngine
- Returns:
- null
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getTupleInfos
public uk.ac.starlink.table.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'snullable
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 interfaceMatchEngine
- Returns:
- array of objects describing the requirements on each element of the tuples used for matching
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getMatchParameters
public uk.ac.starlink.table.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 callingDescribedValue.setValue(java.lang.Object)
on the returned objects.- Specified by:
getMatchParameters
in interfaceMatchEngine
- Returns:
- array of described values which influence the match
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getTuningParameters
public uk.ac.starlink.table.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 callingDescribedValue.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 ofMatchKit.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 interfaceMatchEngine
- Returns:
- array of described values which may influence match performance
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toString
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