1 files changed, 32 insertions, 0 deletions

diff --git a/subprojects/logic/src/main/java/tools/refinery/logic/literal/Literal.java b/subprojects/logic/src/main/java/tools/refinery/logic/literal/Literal.java
new file mode 100644
index 00000000..08a0241c
--- /dev/null
+++ b/subprojects/logic/src/main/java/tools/refinery/logic/literal/Literal.java
@@ -0,0 +1,32 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.logic.literal;
+
+import tools.refinery.logic.equality.LiteralEqualityHelper;
+import tools.refinery.logic.equality.LiteralHashCodeHelper;
+import tools.refinery.logic.substitution.Substitution;
+import tools.refinery.logic.term.Variable;
+
+import java.util.Set;
+
+public interface Literal {
+        Set<Variable> getOutputVariables();
+
+        Set<Variable> getInputVariables(Set<? extends Variable> positiveVariablesInClause);
+
+        Set<Variable> getPrivateVariables(Set<? extends Variable> positiveVariablesInClause);
+
+        Literal substitute(Substitution substitution);
+
+        default Literal reduce() {
+                return this;
+        }
+
+        @SuppressWarnings("BooleanMethodIsAlwaysInverted")
+        boolean equalsWithSubstitution(LiteralEqualityHelper helper, Literal other);
+
+        int hashCodeWithSubstitution(LiteralHashCodeHelper helper);
+}