diff --git a/src/document/change/change.ts b/src/document/change/change.ts
index f33573154..663d4787a 100644
--- a/src/document/change/change.ts
+++ b/src/document/change/change.ts
@@ -17,7 +17,7 @@
 import { ActorID } from '@yorkie-js-sdk/src/document/time/actor_id';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { CRDTRoot } from '@yorkie-js-sdk/src/document/crdt/root';
 import { ChangeID } from '@yorkie-js-sdk/src/document/change/change_id';
@@ -86,17 +86,13 @@ export class Change {
   /**
    * `execute` executes the operations of this change to the given root.
    */
-  public execute(root: CRDTRoot): Array<Modified> {
-    const modifieds: Array<Modified> = [];
+  public execute(root: CRDTRoot): Array<InternalOpInfo> {
+    const opInfos: Array<InternalOpInfo> = [];
     for (const operation of this.operations) {
-      const modified = operation.execute(root);
-      if (Array.isArray(modified)) {
-        modifieds.push(...modified);
-      } else if (modified) {
-        modifieds.push(modified);
-      }
+      const infos = operation.execute(root);
+      opInfos.push(...infos);
     }
-    return modifieds;
+    return opInfos;
   }
 
   /**
diff --git a/src/document/document.ts b/src/document/document.ts
index e8dbb27d6..25008c914 100644
--- a/src/document/document.ts
+++ b/src/document/document.ts
@@ -46,7 +46,7 @@ import {
 } from '@yorkie-js-sdk/src/document/change/checkpoint';
 import { TimeTicket } from '@yorkie-js-sdk/src/document/time/ticket';
 import {
-  Modified,
+  InternalOpInfo,
   OperationInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { JSONObject } from './json/object';
@@ -250,7 +250,7 @@ export class Document<T> {
       }
 
       const change = context.getChange();
-      const modifieds = change.execute(this.root);
+      const internalOpInfos = change.execute(this.root);
       this.localChanges.push(change);
       this.changeID = change.getID();
 
@@ -260,8 +260,8 @@ export class Document<T> {
           value: [
             {
               message: change.getMessage() || '',
-              operations: modifieds.map((modified) =>
-                this.getOperationInfo(modified),
+              operations: internalOpInfos.map((internalOpInfo) =>
+                this.toOperationInfo(internalOpInfo),
               ),
             },
           ],
@@ -603,11 +603,11 @@ export class Document<T> {
 
     const changeInfos: Array<ChangeInfo> = [];
     for (const change of changes) {
-      const modifieds = change.execute(this.root);
+      const inernalOpInfos = change.execute(this.root);
       changeInfos.push({
         message: change.getMessage() || '',
-        operations: modifieds.map((modified) =>
-          this.getOperationInfo(modified),
+        operations: inernalOpInfos.map((opInfo) =>
+          this.toOperationInfo(opInfo),
         ),
       });
       this.changeID = this.changeID.syncLamport(change.getID().getLamport());
@@ -659,14 +659,14 @@ export class Document<T> {
     return pathTrie.findPrefixes().map((element) => element.join('.'));
   }
 
-  private getOperationInfo(modified: Modified): OperationInfo {
+  private toOperationInfo(internalOpInfo: InternalOpInfo): OperationInfo {
     const opInfo = {} as OperationInfo;
-    for (const key of Object.keys(modified)) {
+    for (const key of Object.keys(internalOpInfo)) {
       if (key === 'element') {
-        opInfo.path = this.root.createSubPaths(modified[key])!.join('.');
+        opInfo.path = this.root.createSubPaths(internalOpInfo[key])!.join('.');
       } else {
-        const k = key as keyof Omit<Modified, 'element'>;
-        opInfo[k] = modified[k];
+        const k = key as keyof Omit<InternalOpInfo, 'element'>;
+        opInfo[k] = internalOpInfo[k];
       }
     }
     return opInfo;
diff --git a/src/document/operation/add_operation.ts b/src/document/operation/add_operation.ts
index 597fbd870..9a79b56a1 100644
--- a/src/document/operation/add_operation.ts
+++ b/src/document/operation/add_operation.ts
@@ -21,7 +21,7 @@ import { CRDTRoot } from '@yorkie-js-sdk/src/document/crdt/root';
 import { CRDTArray } from '@yorkie-js-sdk/src/document/crdt/array';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 
 /**
@@ -57,7 +57,7 @@ export class AddOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute(root: CRDTRoot): Modified {
+  public execute(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -69,11 +69,13 @@ export class AddOperation extends Operation {
     const value = this.value.deepcopy();
     array.insertAfter(this.prevCreatedAt, value);
     root.registerElement(value, array);
-    return {
-      type: 'add',
-      element: this.getParentCreatedAt(),
-      index: Number(array.subPathOf(this.getEffectedCreatedAt())),
-    };
+    return [
+      {
+        type: 'add',
+        element: this.getParentCreatedAt(),
+        index: Number(array.subPathOf(this.getEffectedCreatedAt())),
+      },
+    ];
   }
 
   /**
diff --git a/src/document/operation/edit_operation.ts b/src/document/operation/edit_operation.ts
index bdff652c6..e3c52af4f 100644
--- a/src/document/operation/edit_operation.ts
+++ b/src/document/operation/edit_operation.ts
@@ -21,7 +21,7 @@ import { RGATreeSplitNodePos } from '@yorkie-js-sdk/src/document/crdt/rga_tree_s
 import { CRDTText } from '@yorkie-js-sdk/src/document/crdt/text';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { Indexable } from '../document';
 
@@ -79,7 +79,7 @@ export class EditOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute<A extends Indexable>(root: CRDTRoot): Array<Modified> {
+  public execute<A extends Indexable>(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -98,7 +98,7 @@ export class EditOperation extends Operation {
     if (!this.fromPos.equals(this.toPos)) {
       root.registerTextWithGarbage(text);
     }
-    const modified = changes.map(({ type, actor, from, to, value }) => {
+    return changes.map(({ type, actor, from, to, value }) => {
       return type === 'content'
         ? {
             type: 'edit',
@@ -115,8 +115,7 @@ export class EditOperation extends Operation {
             to,
             element: this.getParentCreatedAt(),
           };
-    }) as Array<Modified>;
-    return modified;
+    }) as Array<InternalOpInfo>;
   }
 
   /**
diff --git a/src/document/operation/increase_operation.ts b/src/document/operation/increase_operation.ts
index 1993c2c9a..f38a1b49b 100644
--- a/src/document/operation/increase_operation.ts
+++ b/src/document/operation/increase_operation.ts
@@ -16,7 +16,7 @@
 
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { TimeTicket } from '@yorkie-js-sdk/src/document/time/ticket';
 import { CRDTElement } from '@yorkie-js-sdk/src/document/crdt/element';
@@ -55,7 +55,7 @@ export class IncreaseOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute(root: CRDTRoot): Modified {
+  public execute(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -66,11 +66,13 @@ export class IncreaseOperation extends Operation {
     const counter = parentObject as CRDTCounter;
     const value = this.value.deepcopy() as Primitive;
     counter.increase(value);
-    return {
-      type: 'increase',
-      element: this.getEffectedCreatedAt(),
-      value: value.getValue() as number,
-    };
+    return [
+      {
+        type: 'increase',
+        element: this.getEffectedCreatedAt(),
+        value: value.getValue() as number,
+      },
+    ];
   }
 
   /**
diff --git a/src/document/operation/move_operation.ts b/src/document/operation/move_operation.ts
index ed8ba5a4f..c5b1b57d7 100644
--- a/src/document/operation/move_operation.ts
+++ b/src/document/operation/move_operation.ts
@@ -20,7 +20,7 @@ import { CRDTRoot } from '@yorkie-js-sdk/src/document/crdt/root';
 import { CRDTArray } from '@yorkie-js-sdk/src/document/crdt/array';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 
 /**
@@ -61,7 +61,7 @@ export class MoveOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute(root: CRDTRoot): Modified {
+  public execute(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -73,12 +73,14 @@ export class MoveOperation extends Operation {
     const previousIndex = Number(array.subPathOf(this.createdAt));
     array.moveAfter(this.prevCreatedAt, this.createdAt, this.getExecutedAt());
     const index = Number(array.subPathOf(this.createdAt));
-    return {
-      type: 'move',
-      element: this.getParentCreatedAt(),
-      index,
-      previousIndex,
-    };
+    return [
+      {
+        type: 'move',
+        element: this.getParentCreatedAt(),
+        index,
+        previousIndex,
+      },
+    ];
   }
 
   /**
diff --git a/src/document/operation/operation.ts b/src/document/operation/operation.ts
index ec57d4a05..ae78fce36 100644
--- a/src/document/operation/operation.ts
+++ b/src/document/operation/operation.ts
@@ -89,19 +89,19 @@ export type SelectOpInfo = {
 };
 
 /**
- * `Modified` represents the information of the modified element. It is used to
+ * `InternalOpInfo` represents the information of the operation. It is used to
  * internally and can be converted to `OperationInfo` to inform to the user.
  */
-export type Modified =
-  | OpToModified<AddOpInfo>
-  | OpToModified<IncreaseOpInfo>
-  | OpToModified<RemoveOpInfo>
-  | OpToModified<SetOpInfo>
-  | OpToModified<MoveOpInfo>
-  | OpToModified<EditOpInfo>
-  | OpToModified<StyleOpInfo>
-  | OpToModified<SelectOpInfo>;
-type OpToModified<T extends OperationInfo> = Omit<T, 'path'> & {
+export type InternalOpInfo =
+  | ToInternalOpInfo<AddOpInfo>
+  | ToInternalOpInfo<IncreaseOpInfo>
+  | ToInternalOpInfo<RemoveOpInfo>
+  | ToInternalOpInfo<SetOpInfo>
+  | ToInternalOpInfo<MoveOpInfo>
+  | ToInternalOpInfo<EditOpInfo>
+  | ToInternalOpInfo<StyleOpInfo>
+  | ToInternalOpInfo<SelectOpInfo>;
+type ToInternalOpInfo<T extends OperationInfo> = Omit<T, 'path'> & {
   element: TimeTicket;
 };
 
@@ -152,7 +152,5 @@ export abstract class Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public abstract execute(
-    root: CRDTRoot,
-  ): Array<Modified> | Modified | undefined;
+  public abstract execute(root: CRDTRoot): Array<InternalOpInfo>;
 }
diff --git a/src/document/operation/remove_operation.ts b/src/document/operation/remove_operation.ts
index a12d2f4a1..3f53757c4 100644
--- a/src/document/operation/remove_operation.ts
+++ b/src/document/operation/remove_operation.ts
@@ -19,7 +19,7 @@ import { TimeTicket } from '@yorkie-js-sdk/src/document/time/ticket';
 import { CRDTRoot } from '@yorkie-js-sdk/src/document/crdt/root';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { CRDTContainer } from '@yorkie-js-sdk/src/document/crdt/element';
 import { CRDTArray } from '@yorkie-js-sdk/src/document/crdt/array';
@@ -53,7 +53,7 @@ export class RemoveOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute(root: CRDTRoot): Modified {
+  public execute(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -67,16 +67,20 @@ export class RemoveOperation extends Operation {
     root.registerRemovedElement(elem);
 
     return parentObject instanceof CRDTArray
-      ? {
-          type: 'remove',
-          element: this.getEffectedCreatedAt(),
-          index: Number(key),
-        }
-      : {
-          type: 'remove',
-          element: this.getEffectedCreatedAt(),
-          key,
-        };
+      ? [
+          {
+            type: 'remove',
+            element: this.getEffectedCreatedAt(),
+            index: Number(key),
+          },
+        ]
+      : [
+          {
+            type: 'remove',
+            element: this.getEffectedCreatedAt(),
+            key,
+          },
+        ];
   }
 
   /**
diff --git a/src/document/operation/select_operation.ts b/src/document/operation/select_operation.ts
index 42eef9d19..cd9fc0bd9 100644
--- a/src/document/operation/select_operation.ts
+++ b/src/document/operation/select_operation.ts
@@ -21,7 +21,7 @@ import { RGATreeSplitNodePos } from '@yorkie-js-sdk/src/document/crdt/rga_tree_s
 import { CRDTText } from '@yorkie-js-sdk/src/document/crdt/text';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { Indexable } from '../document';
 
@@ -58,7 +58,7 @@ export class SelectOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute<A extends Indexable>(root: CRDTRoot): Modified | undefined {
+  public execute<A extends Indexable>(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -72,12 +72,14 @@ export class SelectOperation extends Operation {
       this.getExecutedAt(),
     );
     return change
-      ? {
-          ...change,
-          type: 'select',
-          element: this.getParentCreatedAt(),
-        }
-      : undefined;
+      ? [
+          {
+            ...change,
+            type: 'select',
+            element: this.getParentCreatedAt(),
+          },
+        ]
+      : [];
   }
 
   /**
diff --git a/src/document/operation/set_operation.ts b/src/document/operation/set_operation.ts
index 38101b573..3120f6f49 100644
--- a/src/document/operation/set_operation.ts
+++ b/src/document/operation/set_operation.ts
@@ -21,7 +21,7 @@ import { CRDTRoot } from '@yorkie-js-sdk/src/document/crdt/root';
 import { CRDTObject } from '@yorkie-js-sdk/src/document/crdt/object';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 
 /**
@@ -58,7 +58,7 @@ export class SetOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute(root: CRDTRoot): Modified {
+  public execute(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -70,11 +70,13 @@ export class SetOperation extends Operation {
     const value = this.value.deepcopy();
     obj.set(this.key, value);
     root.registerElement(value, obj);
-    return {
-      type: 'set',
-      element: this.getParentCreatedAt(),
-      key: this.key,
-    };
+    return [
+      {
+        type: 'set',
+        element: this.getParentCreatedAt(),
+        key: this.key,
+      },
+    ];
   }
 
   /**
diff --git a/src/document/operation/style_operation.ts b/src/document/operation/style_operation.ts
index a68bee223..76819df4c 100644
--- a/src/document/operation/style_operation.ts
+++ b/src/document/operation/style_operation.ts
@@ -21,7 +21,7 @@ import { RGATreeSplitNodePos } from '@yorkie-js-sdk/src/document/crdt/rga_tree_s
 import { CRDTText } from '@yorkie-js-sdk/src/document/crdt/text';
 import {
   Operation,
-  Modified,
+  InternalOpInfo,
 } from '@yorkie-js-sdk/src/document/operation/operation';
 import { Indexable } from '../document';
 
@@ -68,7 +68,7 @@ export class StyleOperation extends Operation {
   /**
    * `execute` executes this operation on the given `CRDTRoot`.
    */
-  public execute<A extends Indexable>(root: CRDTRoot): Array<Modified> {
+  public execute<A extends Indexable>(root: CRDTRoot): Array<InternalOpInfo> {
     const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
     if (!parentObject) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
@@ -91,7 +91,7 @@ export class StyleOperation extends Operation {
         value,
         element: this.getParentCreatedAt(),
       };
-    }) as Array<Modified>;
+    }) as Array<InternalOpInfo>;
   }
 
   /**