2 files changed, 7 insertions, 1 deletions

diff --git a/subprojects/language/src/main/java/tools/refinery/language/resource/ProblemResourceDescriptionStrategy.java b/subprojects/language/src/main/java/tools/refinery/language/resource/ProblemResourceDescriptionStrategy.java
index 8fd60364..505c7787 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/resource/ProblemResourceDescriptionStrategy.java
+++ b/subprojects/language/src/main/java/tools/refinery/language/resource/ProblemResourceDescriptionStrategy.java
@@ -154,6 +154,9 @@ public class ProblemResourceDescriptionStrategy extends DefaultResourceDescripti
                         if (ProblemUtil.isTypeLike(relation)) {
                                 builder.put(TYPE_LIKE, TYPE_LIKE_TRUE);
                         }
+                } else if (eObject instanceof RuleDefinition) {
+                        // Rule definitions and predicates live in the same namespace.
+                        builder.put(SHADOWING_KEY, SHADOWING_KEY_RELATION);
                 } else if (eObject instanceof AggregatorDeclaration) {
                         builder.put(SHADOWING_KEY, SHADOWING_KEY_AGGREGATOR);
                 }
diff --git a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index 0d35fb03..9f5fdeae 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -170,12 +170,15 @@ public class ProblemValidator extends AbstractProblemValidator {
 
         @Check
         public void checkUniqueDeclarations(Problem problem) {
-                var relations = new ArrayList<Relation>();
+                var relations = new ArrayList<NamedElement>();
                 var nodes = new ArrayList<Node>();
                 var aggregators = new ArrayList<AggregatorDeclaration>();
                 for (var statement : problem.getStatements()) {
                         if (statement instanceof Relation relation) {
                                 relations.add(relation);
+                        } else if (statement instanceof RuleDefinition ruleDefinition) {
+                                // Rule definitions and predicates live in the same namespace.
+                                relations.add(ruleDefinition);
                         } else if (statement instanceof NodeDeclaration nodeDeclaration) {
                                 nodes.addAll(nodeDeclaration.getNodes());
                         } else if (statement instanceof AggregatorDeclaration aggregatorDeclaration) {