diff --git a/src/main/java/com/clevercloud/biscuit/datalog/Scope.java b/src/main/java/com/clevercloud/biscuit/datalog/Scope.java
index 6a9e045c..0658bfde 100644
--- a/src/main/java/com/clevercloud/biscuit/datalog/Scope.java
+++ b/src/main/java/com/clevercloud/biscuit/datalog/Scope.java
@@ -75,4 +75,12 @@ static public Either<Error.FormatError, Scope> deserialize(Schema.Scope scope) {
         }
         return Left(new Error.FormatError.DeserializationError("invalid Scope"));
     }
+
+    @Override
+    public String toString() {
+        return "Scope{" +
+                "kind=" + kind +
+                ", publicKey=" + publicKey +
+                '}';
+    }
 }
diff --git a/src/main/java/com/clevercloud/biscuit/datalog/SymbolTable.java b/src/main/java/com/clevercloud/biscuit/datalog/SymbolTable.java
index b8800f50..6bdeef92 100644
--- a/src/main/java/com/clevercloud/biscuit/datalog/SymbolTable.java
+++ b/src/main/java/com/clevercloud/biscuit/datalog/SymbolTable.java
@@ -61,7 +61,7 @@ private String fromEpochIsoDate(long epochSec) {
             "query"
     );
     public final List<String> symbols;
-    public final List<PublicKey> publicKeys;
+    private final List<PublicKey> publicKeys;
 
     public long insert(final String symbol) {
         int index = this.defaultSymbols.indexOf(symbol);
@@ -81,6 +81,13 @@ public long insert(final String symbol) {
     public int currentOffset() {
         return this.symbols.size();
     }
+    public int currentPublicKeyOffset() {
+        return this.publicKeys.size();
+    }
+
+    public List<PublicKey> publicKeys() {
+        return publicKeys;
+    }
 
     public long insert(final PublicKey publicKey) {
         int index = this.publicKeys.indexOf(publicKey);
@@ -280,9 +287,9 @@ public SymbolTable(SymbolTable s) {
 
     public SymbolTable(List<String> symbols, List<PublicKey> publicKeys) {
         this.symbols = new ArrayList<>();
-        symbols.addAll(symbols);
+        this.symbols.addAll(symbols);
         this.publicKeys = new ArrayList<>();
-        publicKeys.addAll(publicKeys);
+        this.publicKeys.addAll(publicKeys);
     }
 
     public List<String> getAllSymbols() {
diff --git a/src/main/java/com/clevercloud/biscuit/datalog/TrustedOrigins.java b/src/main/java/com/clevercloud/biscuit/datalog/TrustedOrigins.java
index eea8b2d5..8d1d14f2 100644
--- a/src/main/java/com/clevercloud/biscuit/datalog/TrustedOrigins.java
+++ b/src/main/java/com/clevercloud/biscuit/datalog/TrustedOrigins.java
@@ -77,4 +77,11 @@ public static TrustedOrigins fromScopes(List<Scope> ruleScopes,
     public boolean contains(Origin factOrigin) {
         return this.inner.inner.containsAll(factOrigin.inner);
     }
+
+    @Override
+    public String toString() {
+        return "TrustedOrigins{" +
+                "inner=" + inner +
+                '}';
+    }
 }