1 files changed, 18 insertions, 0 deletions

diff --git a/subprojects/store-query/src/main/java/tools/refinery/store/query/substitution/StatelessSubstitution.java b/subprojects/store-query/src/main/java/tools/refinery/store/query/substitution/StatelessSubstitution.java
new file mode 100644
index 00000000..d33ad6fb
--- /dev/null
+++ b/subprojects/store-query/src/main/java/tools/refinery/store/query/substitution/StatelessSubstitution.java
@@ -0,0 +1,18 @@
+package tools.refinery.store.query.substitution;
+
+import tools.refinery.store.query.Variable;
+
+public enum StatelessSubstitution implements Substitution {
+        FAILING {
+                @Override
+                public Variable getSubstitute(Variable variable) {
+                        throw new IllegalArgumentException("No substitute for " + variable);
+                }
+        },
+        IDENTITY {
+                @Override
+                public Variable getSubstitute(Variable variable) {
+                        return variable;
+                }
+        }
+}