diff --git a/package.json b/package.json
index 77e275b..7ae9b88 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@cosmicmind/domainjs",
-  "version": "0.0.1-rc-072224-4",
+  "version": "0.0.1-rc-073024-4",
   "description": "A domain-driven design framework for scalable systems.",
   "keywords": [],
   "author": {
diff --git a/src/Aggregate.ts b/src/Aggregate.ts
index e37f88b..289792e 100644
--- a/src/Aggregate.ts
+++ b/src/Aggregate.ts
@@ -41,11 +41,11 @@ import {
 } from '@/Entity'
 
 import {
-  EventTopics,
-  EventObservable,
-} from '@/Event'
+  Topics,
+  ObservableTopics,
+} from '@/Topic'
 
-export abstract class Aggregate<E extends Entity, T extends EventTopics = EventTopics> extends EventObservable<T> {
+export abstract class Aggregate<E extends Entity, T extends Topics = Topics> extends ObservableTopics<T> {
   protected root: E
 
   constructor(root: E) {
diff --git a/src/Message.ts b/src/Message.ts
new file mode 100644
index 0000000..0ea6559
--- /dev/null
+++ b/src/Message.ts
@@ -0,0 +1,189 @@
+/**
+ * BSD 3-Clause License
+ *
+ * Copyright © 2023, Daniel Jonathan <daniel at cosmicmind dot com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES LOSS OF USE, DATA, OR PROFITS OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @module Message
+ */
+
+import {
+  guard,
+  FoundationError,
+} from '@cosmicmind/foundationjs'
+
+import {
+  Observable,
+  ObservableTopics,
+} from '@cosmicmind/patternjs'
+
+/**
+ * Represents an Message.
+ *
+ * @example
+ * const message: Message = {
+ *   name: 'John Doe',
+ *   age: 25
+ * }
+ */
+export type Message = Record<string, unknown>
+
+/**
+ * Represents a collection of message topics.
+ *
+ * @extends {ObservableTopics}
+ *
+ * @property {Message} [K] - The message topic.
+ */
+export type MessageTopics = ObservableTopics & {
+  readonly [K: string]: Message
+}
+
+/**
+ * An observable class for handling messages of specific types.
+ *
+ * @template T The message topic type.
+ */
+export class MessageObservable<T extends MessageTopics> extends Observable<T> {}
+
+/**
+ * Represents the lifecycle hooks for an message property.
+ *
+ * @template E - The type of the message.
+ * @template V - The type of the property value.
+ */
+export type MessagePropertyLifecycle<E extends Message, V> = {
+  required?: boolean
+  validator?(value: V, message: E): boolean | never
+}
+
+/**
+ * Represents a map that defines the lifecycle of message properties.
+ *
+ * @template E - The type of the message.
+ */
+export type MessagePropertyLifecycleMap<E extends Message> = {
+  [K in keyof E]?: MessagePropertyLifecycle<E, E[K]>
+}
+
+export class MessageError extends FoundationError {}
+
+/**
+ * Represents the lifecycle methods for an message.
+ *
+ * @template E - The type of message.
+ */
+export type MessageLifecycle<E extends Message> = {
+  created?(message: E): void
+  error?(error: MessageError): void
+  properties?: MessagePropertyLifecycleMap<E>
+}
+
+/**
+ * Defines an message with an optional message lifecycle handler.
+ *
+ * @template E The type of the message.
+ * @param {MessageLifecycle<E>} [handler={}] The optional message lifecycle handler.
+ * @returns {(message: E) => E} A function that creates an message with the given lifecycle handler.
+ */
+export const defineMessage = <E extends Message>(handler: MessageLifecycle<E> = {}): (message: E) => E =>
+  (message: E): E => makeMessage(message, handler)
+
+/**
+ * Creates a proxy message handler that prmessages the modification of message properties.
+ *
+ * @template E - The message type.
+ * @param {MessageLifecycle<E>} handler - The message lifecycle handler.
+ * @returns {ProxyHandler<E>} - The proxy message handler.
+ */
+function makeMessageHandler<E extends Message>(handler: MessageLifecycle<E>): ProxyHandler<E> {
+  return {
+    set(): never {
+      throwError('cannot modify message properties', handler)
+    },
+  }
+}
+
+/**
+ * Throws an MessageError with a specified message and invokes the error handler.
+ *
+ * @template E - The type of Message.
+ * @param {string} message - The error message.
+ * @param {MessageLifecycle<E>} handler - The message lifecycle handler.
+ * @throws {MessageError} - The MessageError instance.
+ * @return {never} - This method never returns.
+ */
+function throwError<E extends Message>(message: string, handler: MessageLifecycle<E>): never {
+  const error = new MessageError(message)
+  handler.error?.(error)
+  throw error
+}
+
+/**
+ * Creates an message of type `E`.
+ *
+ * @template E - The type of the message to create.
+ * @param {E} target - The target object to create the message from.
+ * @param {MessageLifecycle<E>} [handler={}] - The lifecycle handler for the message.
+ * @returns {E} - The created message object.
+ * @throws {MessageError} - If the target object is invalid.
+ */
+function makeMessage<E extends Message>(target: E, handler: MessageLifecycle<E> = {}): E | never {
+  if (guard<E>(target)) {
+    const properties = handler.properties
+
+    if (guard<MessagePropertyLifecycleMap<E>>(properties)) {
+      const message = new Proxy(target, makeMessageHandler(handler))
+
+      for (const [ key, property ] of Object.entries(properties) as [string, MessagePropertyLifecycle<E, unknown>][]) {
+        if (property.required) {
+          if (!(key in target)) {
+            throwError(`${JSON.stringify(target)} ${key} is required`, handler)
+          }
+
+          if (false === property.validator?.(target[key], message)) {
+            throwError(`${JSON.stringify(target)} ${key} is invalid`, handler)
+          }
+        }
+        else if (key in target && 'undefined' !== typeof target[key]) {
+          if (guard(property, 'validator') && false === property.validator?.(target[key], message)) {
+            throwError(`${JSON.stringify(target)} ${key} is invalid`, handler)
+          }
+        }
+      }
+
+      handler.created?.(message)
+
+      return message
+    }
+  }
+
+  throw new MessageError(`${String(target)} is invalid`)
+}
\ No newline at end of file
diff --git a/src/Topic.ts b/src/Topic.ts
index 90b219e..b6d6806 100644
--- a/src/Topic.ts
+++ b/src/Topic.ts
@@ -35,28 +35,10 @@
  */
 
 import {
-  Observable,
-  ObservableTopics,
+  Observable as O,
+  ObservableTopics as OT,
 } from '@cosmicmind/patternjs'
 
-import {
-  Event,
-} from '@/Event'
+export type Topics = OT
 
-/**
- * Represents a collection of Event topics.
- *
- * @extends {ObservableTopics}
- *
- * @property {Event} [K] - A event topic.
- */
-export type EventTopics = ObservableTopics & {
-  readonly [K: string]: Event
-}
-
-/**
- * An observable class for handling topics of specific types.
- *
- * @template T The event topic type.
- */
-export class TopicObservable<T extends EventTopics> extends Observable<T> {}
+export class ObservableTopics<T extends Topics> extends O<T> {}
diff --git a/src/index.ts b/src/index.ts
index 0a15afc..61aabf3 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -33,4 +33,6 @@
 export * from '@/Aggregate'
 export * from '@/Event'
 export * from '@/Entity'
+export * from '@/Message'
+export * from '@/Topic'
 export * from '@/Value'
\ No newline at end of file