diff --git a/src/DigitalData.EmailProfiler.Domain/Common/BaseEntity.cs b/src/DigitalData.EmailProfiler.Domain/Common/BaseEntity.cs
new file mode 100644
index 0000000..50e7d15
--- /dev/null
+++ b/src/DigitalData.EmailProfiler.Domain/Common/BaseEntity.cs
@@ -0,0 +1,9 @@
+namespace DigitalData.EmailProfiler.Domain.Common;
+
+public abstract class BaseEntity
+{
+    public DateTime? CreatedDate { get; set; }
+    public string? CreatedBy { get; set; }
+    public DateTime? ModifiedDate { get; set; }
+    public string? ModifiedBy { get; set; }
+}
diff --git a/src/DigitalData.EmailProfiler.Domain/Common/IAggregateRoot.cs b/src/DigitalData.EmailProfiler.Domain/Common/IAggregateRoot.cs
new file mode 100644
index 0000000..a7bdc76
--- /dev/null
+++ b/src/DigitalData.EmailProfiler.Domain/Common/IAggregateRoot.cs
@@ -0,0 +1,8 @@
+namespace DigitalData.EmailProfiler.Domain.Common;
+
+/// <summary>
+/// Marker interface for aggregate roots in DDD
+/// </summary>
+public interface IAggregateRoot
+{
+}
diff --git a/src/DigitalData.EmailProfiler.Domain/Common/ValueObject.cs b/src/DigitalData.EmailProfiler.Domain/Common/ValueObject.cs
new file mode 100644
index 0000000..f741767
--- /dev/null
+++ b/src/DigitalData.EmailProfiler.Domain/Common/ValueObject.cs
@@ -0,0 +1,43 @@
+namespace DigitalData.EmailProfiler.Domain.Common;
+
+/// <summary>
+/// Base class for value objects that implement equality by value
+/// </summary>
+public abstract class ValueObject
+{
+    protected abstract IEnumerable<object> GetEqualityComponents();
+
+    public override bool Equals(object? obj)
+    {
+        if (obj == null || obj.GetType() != GetType())
+        {
+            return false;
+        }
+
+        var other = (ValueObject)obj;
+        return GetEqualityComponents().SequenceEqual(other.GetEqualityComponents());
+    }
+
+    public override int GetHashCode()
+    {
+        return GetEqualityComponents()
+            .Select(x => x?.GetHashCode() ?? 0)
+            .Aggregate((x, y) => x ^ y);
+    }
+
+    public static bool operator ==(ValueObject? left, ValueObject? right)
+    {
+        if (left is null && right is null)
+            return true;
+
+        if (left is null || right is null)
+            return false;
+
+        return left.Equals(right);
+    }
+
+    public static bool operator !=(ValueObject? left, ValueObject? right)
+    {
+        return !(left == right);
+    }
+}