diff --git a/src/models/formulas/InFormula.java b/src/models/formulas/InFormula.java
new file mode 100644
index 0000000..7b95536
--- /dev/null
+++ b/src/models/formulas/InFormula.java
@@ -0,0 +1,36 @@
+package models.formulas;
+
+import lombok.Getter;
+import models.terms.EvaluatableTerm;
+
+@Getter
+public class InFormula extends Formula {
+
+	private EvaluatableTerm leftSideHand;
+	private EvaluatableTerm rightSideHand;
+	
+	public InFormula(EvaluatableTerm leftSideHand, EvaluatableTerm rightSideHand) {
+		this.leftSideHand = leftSideHand;
+		this.rightSideHand = rightSideHand;
+	}
+	
+	@Override
+	public String toString() {
+		return leftSideHand.toString() + " in " + rightSideHand.toString();
+	}
+
+	@Override
+	public boolean equals(Object another) {
+		if (! (another instanceof InFormula)) {
+			return false;
+		}
+		InFormula formula = (InFormula) another;
+		return leftSideHand.equals(formula.getLeftSideHand()) && rightSideHand.equals(formula.getRightSideHand());
+	}
+
+	@Override
+	public int hashCode() {
+		return toString().hashCode();
+	}
+
+}
diff --git a/src/models/formulas/meta/MetaFormula.java b/src/models/formulas/meta/MetaFormula.java
index 949217f..cd43fbd 100644
--- a/src/models/formulas/meta/MetaFormula.java
+++ b/src/models/formulas/meta/MetaFormula.java
@@ -17,7 +17,7 @@
 	public abstract boolean isMatchedBy(Formula formula, Map<Variable, RDLTerm> binding, Map<Variable, OrderVariableConstraint> orderConstraint);
 	
 	public abstract String toString();
-	public abstract boolean equals(Object anohter);
+	public abstract boolean equals(Object another);
 	public abstract int hashCode();
 	
 }
diff --git a/src/models/formulas/meta/MetaInFormula.java b/src/models/formulas/meta/MetaInFormula.java
new file mode 100644
index 0000000..d446557
--- /dev/null
+++ b/src/models/formulas/meta/MetaInFormula.java
@@ -0,0 +1,61 @@
+package models.formulas.meta;
+
+import java.util.Map;
+
+import exceptions.IllegalTypeException;
+import lombok.Getter;
+import models.algebra.Variable;
+import models.formulas.Formula;
+import models.formulas.InFormula;
+import models.terms.RDLTerm;
+import models.terms.meta.MetaRDLTerm;
+import models.terms.meta.OrderVariableConstraint;
+
+@Getter
+public class MetaInFormula extends MetaFormula {
+
+	private MetaRDLTerm leftSideHand;
+	private MetaRDLTerm rightSideHand;
+	
+	public MetaInFormula(MetaRDLTerm leftSideHand, MetaRDLTerm rightSideHand) {
+		if (! leftSideHand.isEvaluatableTerm()) {
+			throw new IllegalTypeException();
+		}
+		if(! rightSideHand.isEvaluatableTerm()) {
+			throw new IllegalTypeException();
+		}
+		this.leftSideHand = leftSideHand;
+		this.rightSideHand = rightSideHand;
+	}
+	
+	@Override
+	public boolean isMatchedBy(Formula formula, Map<Variable, RDLTerm> binding,
+			Map<Variable, OrderVariableConstraint> orderConstraint) {
+		if (! (formula instanceof InFormula)) {
+			return false;
+		}
+		InFormula inFormula = (InFormula) formula;
+		return leftSideHand.isMatchedBy(inFormula.getLeftSideHand(), binding, orderConstraint) 
+				&& rightSideHand.isMatchedBy(inFormula.getRightSideHand(), binding, orderConstraint);
+	}
+
+	@Override
+	public String toString() {
+		return leftSideHand.toString() + " in " + rightSideHand.toString();
+	}
+
+	@Override
+	public boolean equals(Object anohter) {
+		if (! (anohter instanceof MetaInFormula)) {
+			return false;
+		}
+		MetaInFormula formula = (MetaInFormula) anohter;
+		return leftSideHand.equals(formula.getLeftSideHand()) && rightSideHand.equals(formula.getRightSideHand());
+	}
+
+	@Override
+	public int hashCode() {
+		return toString().hashCode();
+	}
+
+}