diff --git a/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/model/retrievable/attributes/ScoreAttribute.kt b/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/model/retrievable/attributes/ScoreAttribute.kt
index 21e277c6..173ee12c 100644
--- a/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/model/retrievable/attributes/ScoreAttribute.kt
+++ b/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/model/retrievable/attributes/ScoreAttribute.kt
@@ -8,21 +8,36 @@ import kotlin.math.max
  * Scores are expected to be in the range of [0, 1].
  *
  * @author Luca Rossetto
- * @version 1.0.0
+ * @author Ralph Gasser
+ * @version 1.1.0
  */
-data class ScoreAttribute(val score: Float) : MergingRetrievableAttribute {
+sealed interface ScoreAttribute : MergingRetrievableAttribute {
 
-    companion object {
-        val ZERO = ScoreAttribute(0f)
-    }
+    /** The score associated with this [ScoreAttribute]. */
+    val score: Float
 
-    constructor(score: Double) : this(score.toFloat())
+    /**
+     * A similarity score. Strictly bound between 0 and 1.
+     */
+    data class Similarity(override val score: Float): ScoreAttribute {
+        init {
+            require(score in 0f..1f) { "Similarity score '$score' outside of valid range (0, 1)" }
+        }
 
-    init {
-        require(score in 0f..1f) { "Score '$score' outside of valid range (0, 1)" }
+        override fun merge(other: MergingRetrievableAttribute): Similarity = Similarity(
+            max(this.score, (other as? Similarity)?.score ?: 0f)
+        )
     }
 
-    override fun merge(other: MergingRetrievableAttribute): ScoreAttribute = ScoreAttribute(
-        max(this.score, (other as? ScoreAttribute)?.score ?: 0f)
-    )
+    /**
+     * An unbound score. Strictly bound between 0 and 1.
+     */
+    data class Unbound(override val score: Float): ScoreAttribute {
+        init {
+            require(this.score >= 0f) { "Score '$score' outside of valid range (>= 0)." }
+        }
+        override fun merge(other: MergingRetrievableAttribute): Unbound = Unbound(
+            max(this.score, (other as? Unbound)?.score ?: 0f)
+        )
+    }
 }
diff --git a/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/util/math/ScoringFunctions.kt b/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/util/math/ScoringFunctions.kt
index 839241df..7222536c 100644
--- a/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/util/math/ScoringFunctions.kt
+++ b/vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/util/math/ScoringFunctions.kt
@@ -19,7 +19,7 @@ object ScoringFunctions {
      * @param max Maximum value. Default is 1.0.
      */
     fun max(retrieved: Retrieved, max: Float = 1.0f): ScoreAttribute {
-        val distance = retrieved.filteredAttribute<DistanceAttribute>()?.distance ?: return ScoreAttribute.ZERO
-        return ScoreAttribute(max - distance)
+        val distance = retrieved.filteredAttribute<DistanceAttribute>()?.distance ?: return ScoreAttribute.Unbound(0.0f)
+        return ScoreAttribute.Unbound(max - distance)
     }
 }
\ No newline at end of file
diff --git a/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/string/StringDescriptorReader.kt b/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/string/StringDescriptorReader.kt
index a65b1670..45483618 100644
--- a/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/string/StringDescriptorReader.kt
+++ b/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/string/StringDescriptorReader.kt
@@ -47,7 +47,7 @@ class StringDescriptorReader(field: Schema.Field<*, StringDescriptor>, connectio
             val retrievableId = tuple.asUuidValue(RETRIEVABLE_ID_COLUMN_NAME)?.value ?: throw IllegalArgumentException("The provided tuple is missing the required field '${RETRIEVABLE_ID_COLUMN_NAME}'.")
             val score = tuple.asDouble(SCORE_COLUMN_NAME) ?: 0.0
             val retrieved = Retrieved(retrievableId, null, false)
-            retrieved.addAttribute(ScoreAttribute(score))
+            retrieved.addAttribute(ScoreAttribute.Unbound(score.toFloat()))
             retrieved
         }
     }
diff --git a/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/struct/StructDescriptorReader.kt b/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/struct/StructDescriptorReader.kt
index 05ffa440..1b2eab53 100644
--- a/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/struct/StructDescriptorReader.kt
+++ b/vitrivr-engine-module-cottontaildb/src/main/kotlin/org/vitrivr/engine/plugin/cottontaildb/descriptors/struct/StructDescriptorReader.kt
@@ -65,7 +65,7 @@ class StructDescriptorReader(field: Schema.Field<*, StructDescriptor>, connectio
             val retrievableId = tuple.asUuidValue(RETRIEVABLE_ID_COLUMN_NAME)?.value ?: throw IllegalArgumentException("The provided tuple is missing the required field '${RETRIEVABLE_ID_COLUMN_NAME}'.")
             val score = tuple.asDouble(SCORE_COLUMN_NAME) ?: 0.0
             val retrieved = Retrieved(retrievableId, null, false)
-            retrieved.addAttribute(ScoreAttribute(score))
+            retrieved.addAttribute(ScoreAttribute.Unbound(score.toFloat()))
             retrieved
         }
     }
diff --git a/vitrivr-engine-module-features/src/main/kotlin/org/vitrivr/engine/base/features/averagecolor/AverageColorRetriever.kt b/vitrivr-engine-module-features/src/main/kotlin/org/vitrivr/engine/base/features/averagecolor/AverageColorRetriever.kt
index 2a986f59..e93a5888 100644
--- a/vitrivr-engine-module-features/src/main/kotlin/org/vitrivr/engine/base/features/averagecolor/AverageColorRetriever.kt
+++ b/vitrivr-engine-module-features/src/main/kotlin/org/vitrivr/engine/base/features/averagecolor/AverageColorRetriever.kt
@@ -36,7 +36,7 @@ class AverageColorRetriever(
     override fun toFlow(scope: CoroutineScope) = flow {
         val reader = this@AverageColorRetriever.field.getReader()
         reader.getAll(this@AverageColorRetriever.query).forEach {
-            it.addAttribute(ScoreAttribute(scoringFunction(it)))
+            it.addAttribute(ScoreAttribute.Similarity(scoringFunction(it)))
             emit(it)
         }
     }
diff --git a/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/TemporalSequenceAggregator.kt b/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/TemporalSequenceAggregator.kt
index 1cf1f57b..a063bd9f 100644
--- a/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/TemporalSequenceAggregator.kt
+++ b/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/TemporalSequenceAggregator.kt
@@ -195,7 +195,7 @@ class TemporalSequenceAggregator(
                 id, "temporalSequence", true
             )
 
-            retrieved.addAttribute(ScoreAttribute(score))
+            retrieved.addAttribute(ScoreAttribute.Unbound(score))
             retrieved.addAttribute(RelationshipAttribute(relationships))
 
             emit(retrieved)
diff --git a/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/WeightedScoreFusion.kt b/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/WeightedScoreFusion.kt
index b4c27d1d..139bcc4a 100644
--- a/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/WeightedScoreFusion.kt
+++ b/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/aggregate/WeightedScoreFusion.kt
@@ -70,7 +70,7 @@ class WeightedScoreFusion(
                 //make a copy and override score
                 val retrieved = first.copy()
                 retrieved.filteredAttribute<ScoreAttribute>()
-                retrieved.addAttribute(ScoreAttribute(score))
+                retrieved.addAttribute(ScoreAttribute.Unbound(score))
 
                 emit(retrieved)
 
diff --git a/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/transform/ScoreAggregator.kt b/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/transform/ScoreAggregator.kt
index cc85f22b..2144127f 100644
--- a/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/transform/ScoreAggregator.kt
+++ b/vitrivr-engine-query/src/main/kotlin/org/vitrivr/engine/query/transform/ScoreAggregator.kt
@@ -46,10 +46,10 @@ class ScoreAggregator(
                     }
                 }
 
-                retrieved.addAttribute(ScoreAttribute(score))
+                retrieved.addAttribute(ScoreAttribute.Unbound(score))
 
             } else {
-                retrieved.addAttribute(ScoreAttribute(0f))
+                retrieved.addAttribute(ScoreAttribute.Unbound(0f))
             }
 
             retrieved