Merge pull request #40 from OwnYourData/fix_bucket_ranges

Bucket ranges adjusted to leave no gaps

Author: paul2803-byte

src/main/java/com/example/anonymization/service/FaltJsonService.java

@@ -2,7 +2,6 @@
 
 import com.example.anonymization.data.QueryService;
 import com.example.anonymization.entities.Configuration;
-import com.example.anonymization.exceptions.AnonymizationException;
 import com.example.anonymization.exceptions.RequestModelException;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;

src/main/java/com/example/anonymization/service/anonymizer/Generalization.java

@@ -38,6 +38,7 @@ public void applyAnonymization() {
     }
 
     protected abstract List<Pair<Resource, T>> getSortedValues(Map<Resource, RDFNode> data);
+    protected abstract T getMedianValue(T value1, T value2);
 
     protected Map<Resource, Resource> getRanges(
             List<Pair<Resource, T>> sortedValues,
@@ -98,9 +99,16 @@ protected List<Resource> createBuckets(
     }
 
     protected List<T> getBucketRange(List<Pair<Resource, T>> sortedValues, int bucketNumber, int nrOfBuckets) {
-        return List.of(
-            sortedValues.get(bucketNumber * sortedValues.size() / nrOfBuckets).getRight(),
-            sortedValues.get(((bucketNumber + 1) * sortedValues.size() / nrOfBuckets) - 1).getRight()
+        int lowerBoundIndex = bucketNumber * sortedValues.size() / nrOfBuckets;
+        T lowerBound = getMedianValue(
+                lowerBoundIndex > 0 ? sortedValues.get(lowerBoundIndex - 1).getRight() : null,
+                sortedValues.get(lowerBoundIndex).getRight()
         );
+        int upperBoundIndex = ((bucketNumber + 1) * sortedValues.size() / nrOfBuckets) - 1;
+        T upperBound = getMedianValue(
+                sortedValues.get(upperBoundIndex).getRight(),
+                upperBoundIndex + 1 < sortedValues.size() ? sortedValues.get(upperBoundIndex + 1).getRight() : null
+        );
+        return List.of(lowerBound, upperBound);
     }
 }

src/main/java/com/example/anonymization/service/anonymizer/GeneralizationDate.java

@@ -30,6 +30,22 @@ protected List<Pair<Resource, Calendar>> getSortedValues(Map<Resource, RDFNode>
                 .toList();
     }
 
+    @Override
+    protected Calendar getMedianValue(Calendar value1, Calendar value2) {
+        if (value1 == null) {
+            return value2;
+        }
+        if (value2 == null) {
+            return value1;
+        }
+        long time1 = value1.getTimeInMillis();
+        long time2 = value2.getTimeInMillis();
+        long medianTime = (time1 + time2) / 2;
+        Calendar medianCalendar = Calendar.getInstance();
+        medianCalendar.setTimeInMillis(medianTime);
+        return medianCalendar;
+    }
+
     private static Calendar toDate(RDFNode node) {
         try {
             XSDDateTime xsdDateTime = (XSDDateTime) XSDDatatype.XSDdate.parse(node.asLiteral().getString());

src/main/java/com/example/anonymization/service/anonymizer/GeneralizationNumeric.java

@@ -33,4 +33,15 @@ protected List<Pair<Resource, Double>> getSortedValues(Map<Resource, RDFNode> da
             throw new IllegalArgumentException("Error while parsing numeric values for generalization.", e);
         }
     }
+
+    @Override
+    protected Double getMedianValue(Double value1, Double value2) {
+        if (value1 == null) {
+            return value2;
+        }
+        if (value2 == null) {
+            return value1;
+        }
+        return (value1 + value2) / 2.0;
+    }
 }