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java.lang.Objectuk.ac.starlink.table.join.EqualsMatchEngine
Match engine which considers two rows matched if they contain objects which are non-blank and equal. The objects will typically be strings, but could equally be something else. Match scores are always either 0.0 (equal) or -1.0 (unequal).
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.
Field Summary |
Fields inherited from interface uk.ac.starlink.table.join.MatchEngine |
NO_BINS |
Constructor Summary | |
EqualsMatchEngine()
|
Method Summary | |
boolean |
canBoundMatch()
Indicates that the getMatchBounds(java.lang.Comparable[], java.lang.Comparable[]) method can be invoked
to provide some sort of useful result. |
Object[] |
getBins(Object[] tuple)
Returns a set of keys for bins into which possible matches for a given tuple might fall. |
Comparable[][] |
getMatchBounds(Comparable[] min,
Comparable[] max)
Given a range of tuple values, returns a range outside which no match to anything within that range can result. |
DescribedValue[] |
getMatchParameters()
Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria. |
ValueInfo |
getMatchScoreInfo()
The match score is uninteresting, since it's either -1 or 0. |
ValueInfo[] |
getTupleInfos()
Returns a set of ValueInfo objects indicating what is required for the elements of each tuple. |
double |
matchScore(Object[] tuple1,
Object[] tuple2)
Indicates whether two tuples count as matching each other, and if so how closely. |
String |
toString()
|
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
public EqualsMatchEngine()
Method Detail |
public double matchScore(Object[] tuple1, Object[] tuple2)
MatchEngine
If there's no reason to do otherwise, the range 0..1 is recommended for successul matches. However, if the result has some sort of physical meaning (such as a distance in real space) that may be used instead.
matchScore
in interface MatchEngine
tuple1
- one tupletuple2
- the other tuple
public Object[] getBins(Object[] tuple)
MatchEngine
getBins
in interface MatchEngine
tuple
- tuple
public ValueInfo getMatchScoreInfo()
null
here.
getMatchScoreInfo
in interface MatchEngine
public ValueInfo[] getTupleInfos()
MatchEngine
getTupleInfos
in interface MatchEngine
public DescribedValue[] getMatchParameters()
MatchEngine
DescribedValue.setValue(java.lang.Object)
on the
returned objects.
getMatchParameters
in interface MatchEngine
public boolean canBoundMatch()
MatchEngine
MatchEngine.getMatchBounds(java.lang.Comparable[], java.lang.Comparable[])
method can be invoked
to provide some sort of useful result.
canBoundMatch
in interface MatchEngine
public Comparable[][] getMatchBounds(Comparable[] min, Comparable[] max)
MatchEngine
Both the input and output rectangles are specified by tuples representing its opposite corners; equivalently, they are the minimum and maximum values of each tuple element. In either the input or output min/max tuples, any element may be null to indicate that no information is available on the bounds of that tuple element (coordinate).
This method can be used by match algorithms which know in advance the range of coordinates they will match against and wish to reduce workload by not attempting matches which are bound to fail.
For example, a 1-d Cartesian match engine with an isotropic match error 0.5 would turn input values of ((0,200),(10,210)) into output values ((-0.5,199.5),(10.5,210.5)).
This method will only be called if MatchEngine.canBoundMatch()
returns true. Thus engines that cannot provide any useful
information along these lines (for instance because none of its
tuple elements is Comparable
do not need to
implement it in a meaningful way.
getMatchBounds
in interface MatchEngine
min
- tuple consisting of the minimum values of each
tuple element in a possible match
(to put it another way - coordinates of one corner of a
tuple-space rectangle containing such a match)max
- tuple consisting of the maximum values of each
tuple element in a possible match
(to put it another way - coordinates of the other corner of a
tuple-space rectangle containing such a match)
MatchEngine.canBoundMatch()
public String toString()
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Copyright © 2004 CLRC: Central Laboratory of the Research Councils. All rights reserved. | |||||||||
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