diff --git a/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/ReadableHttpPostsAPI.kt b/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/ReadableHttpPostsAPI.kt
index ac9162d8..c23a1eca 100644
--- a/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/ReadableHttpPostsAPI.kt
+++ b/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/ReadableHttpPostsAPI.kt
@@ -20,20 +20,20 @@ class ReadableHttpPostsAPI(
     private val postsByDatesAddress = "$baseAddress/$getPostsByDatesAddress"
     private val postsByPaginationAddress = "$baseAddress/$getPostsByPaginationAddress"
 
-    override suspend fun getPostById(id: PostId): Post? {
-        return client.post<SimplePost>(postByIdAddress) {
+    override suspend fun getPostById(id: PostId): RegisteredPost? {
+        return client.post<SimpleRegisteredPost>(postByIdAddress) {
             body = id
         }
     }
 
-    override suspend fun getPostsByContent(id: ContentId): List<Post> {
-        return client.post<List<SimplePost>>(postsByContentIdAddress) {
+    override suspend fun getPostsByContent(id: ContentId): List<RegisteredPost> {
+        return client.post<List<SimpleRegisteredPost>>(postsByContentIdAddress) {
             body = id
         }
     }
 
-    override suspend fun getPostsByDates(from: DateTime?, to: DateTime?): List<Post> {
-        return client.post<List<SimplePost>>(postsByDatesAddress) {
+    override suspend fun getPostsByDates(from: DateTime?, to: DateTime?): List<RegisteredPost> {
+        return client.post<List<SimpleRegisteredPost>>(postsByDatesAddress) {
             body = DateTimeRequest(
                 from ?.millis,
                 to ?.millis
@@ -41,8 +41,8 @@ class ReadableHttpPostsAPI(
         }
     }
 
-    override suspend fun getPostsByPagination(pagination: Pagination): PaginationResult<out Post> {
-        return client.post<PaginationResult<SimplePost>>(postsByPaginationAddress) {
+    override suspend fun getPostsByPagination(pagination: Pagination): PaginationResult<out RegisteredPost> {
+        return client.post<PaginationResult<SimpleRegisteredPost>>(postsByPaginationAddress) {
             body = pagination
         }
     }
diff --git a/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/WritableHttpPostsAPI.kt b/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/WritableHttpPostsAPI.kt
index 93d7ee64..15a15fd3 100644
--- a/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/WritableHttpPostsAPI.kt
+++ b/ClientPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/client/WritableHttpPostsAPI.kt
@@ -20,17 +20,17 @@ class WritableHttpPostsAPI(
         port,
         "/$url"
     ) {
-        Json.plain.parse(SimplePost.serializer(), it)
+        Json.plain.parse(SimpleRegisteredPost.serializer(), it)
     }
 
-    override val postCreatedFlow: Flow<Post> = postEventFlow(eventPostsCreatedAddress)
-    override val postDeletedFlow: Flow<Post> = postEventFlow(eventPostsDeletedAddress)
-    override val postUpdatedFlow: Flow<Post> = postEventFlow(eventPostsUpdatedAddress)
+    override val postCreatedFlow: Flow<RegisteredPost> = postEventFlow(eventPostsCreatedAddress)
+    override val postDeletedFlow: Flow<RegisteredPost> = postEventFlow(eventPostsDeletedAddress)
+    override val postUpdatedFlow: Flow<RegisteredPost> = postEventFlow(eventPostsUpdatedAddress)
 
-    override suspend fun createPost(content: PostContents): Post? = client.post<SimplePost>(
+    override suspend fun createPost(post: Post): RegisteredPost? = client.post<SimpleRegisteredPost>(
         createPostAddress
     ) {
-        body = content
+        body = post.content
     }
 
     override suspend fun deletePost(id: PostId): Boolean = client.post(deletePostAddress) {
@@ -39,8 +39,8 @@ class WritableHttpPostsAPI(
 
     override suspend fun updatePostContent(
         postId: PostId,
-        content: PostContents
+        post: Post
     ): Boolean = client.post(createPostAddress) {
-        body = UpdatePostRequest(postId, content)
+        body = UpdatePostRequest(postId, post.content)
     }
 }
\ No newline at end of file
diff --git a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt
index eb001bce..b0bdbeea 100644
--- a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt
+++ b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt
@@ -1,17 +1,16 @@
 package com.insanusmokrassar.postssystem.core.api
 
-import com.insanusmokrassar.postssystem.core.post.Post
-import com.insanusmokrassar.postssystem.core.post.PostId
 import com.insanusmokrassar.postssystem.core.content.ContentId
+import com.insanusmokrassar.postssystem.core.post.*
 import com.insanusmokrassar.postssystem.core.utils.pagination.*
 import com.insanusmokrassar.postssystem.core.utils.pagination.Pagination
 import com.insanusmokrassar.postssystem.core.utils.pagination.PaginationResult
 import org.joda.time.DateTime
 
 interface ReadPostsAPI {
-    suspend fun getPostById(id: PostId): Post?
-    suspend fun getPostsByContent(id: ContentId): List<Post>
-    suspend fun getPostsByDates(from: DateTime? = null, to: DateTime? = null): List<Post>
+    suspend fun getPostById(id: PostId): RegisteredPost?
+    suspend fun getPostsByContent(id: ContentId): List<RegisteredPost>
+    suspend fun getPostsByDates(from: DateTime? = null, to: DateTime? = null): List<RegisteredPost>
 
-    suspend fun getPostsByPagination(pagination: Pagination): PaginationResult<out Post>
+    suspend fun getPostsByPagination(pagination: Pagination): PaginationResult<out RegisteredPost>
 }
\ No newline at end of file
diff --git a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt
index 43b2897c..881120b2 100644
--- a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt
+++ b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt
@@ -5,12 +5,12 @@ import com.insanusmokrassar.postssystem.core.post.*
 import kotlinx.coroutines.flow.Flow
 
 interface WritePostsAPI {
-    val postCreatedFlow: Flow<Post>
-    val postDeletedFlow: Flow<Post>
-    val postUpdatedFlow: Flow<Post>
+    val postCreatedFlow: Flow<RegisteredPost>
+    val postDeletedFlow: Flow<RegisteredPost>
+    val postUpdatedFlow: Flow<RegisteredPost>
 
-    suspend fun createPost(content: PostContents): Post?
+    suspend fun createPost(post: Post): RegisteredPost?
     suspend fun deletePost(id: PostId): Boolean
 
-    suspend fun updatePostContent(postId: PostId, content: PostContents): Boolean
+    suspend fun updatePostContent(postId: PostId, post: Post): Boolean
 }
\ No newline at end of file
diff --git a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt
index 69ed6956..c5f4c4b6 100644
--- a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt
+++ b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt
@@ -2,6 +2,8 @@ package com.insanusmokrassar.postssystem.core.content
 
 typealias ContentId = String
 
-interface Content {
+interface Content
+
+interface RegisteredContent : Content {
     val id: ContentId
 }
diff --git a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/TextContent.kt b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/TextContent.kt
index 3dae566d..af2608e6 100644
--- a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/TextContent.kt
+++ b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/TextContent.kt
@@ -1,5 +1,20 @@
 package com.insanusmokrassar.postssystem.core.content
 
+import kotlinx.serialization.Serializable
+
 interface TextContent : Content {
     val text: String
-}
\ No newline at end of file
+}
+
+interface TextRegisteredContent : RegisteredContent, TextContent
+
+@Serializable
+data class SimpleTextContent(
+    override val text: String
+) : TextContent
+
+@Serializable
+data class SimpleTextRegisteredContent(
+    override val id: ContentId,
+    override val text: String
+) : TextRegisteredContent
diff --git a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt
index f2cec695..2e4b6e29 100644
--- a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt
+++ b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt
@@ -1,21 +1,36 @@
 package com.insanusmokrassar.postssystem.core.post
 
 import com.insanusmokrassar.postssystem.core.content.Content
+import com.insanusmokrassar.postssystem.core.content.RegisteredContent
 import kotlinx.serialization.Serializable
+import org.joda.time.DateTime
 
 typealias PostId = String
 typealias PostContents = List<Content>
+typealias RegisteredPostContents = List<RegisteredContent>
 
 interface Post {
-    val id: PostId
     val content: PostContents
+}
 
-    val meta: PostMetaInfo
+interface RegisteredPost : Post {
+    val id: PostId
+
+    override val content: RegisteredPostContents
+
+    val creationDate: DateTime
+    val modificationDate: DateTime
 }
 
 @Serializable
 data class SimplePost(
-    override val id: PostId,
-    override val content: PostContents,
-    override val meta: PostMetaInfo
+    override val content: PostContents
 ) : Post
+
+@Serializable
+data class SimpleRegisteredPost(
+    override val id: PostId,
+    override val content: RegisteredPostContents,
+    override val creationDate: DateTime,
+    override val modificationDate: DateTime = creationDate
+) : RegisteredPost
\ No newline at end of file
diff --git a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/PostMetaInfo.kt b/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/PostMetaInfo.kt
deleted file mode 100644
index f6133d6c..00000000
--- a/Core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/PostMetaInfo.kt
+++ /dev/null
@@ -1,9 +0,0 @@
-package com.insanusmokrassar.postssystem.core.post
-
-import org.joda.time.DateTime
-
-interface PostMetaInfo {
-    val postId: PostId
-    val creationDate: DateTime
-    val modificationDate: DateTime
-}
\ No newline at end of file
diff --git a/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/Commons.kt b/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/Commons.kt
index b2355b1d..ec03f14d 100644
--- a/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/Commons.kt
+++ b/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/Commons.kt
@@ -1,7 +1,7 @@
 package com.insanusmokrassar.postssystem.core.server
 
 import com.insanusmokrassar.postssystem.core.post.Post
-import com.insanusmokrassar.postssystem.core.post.SimplePost
+import com.insanusmokrassar.postssystem.core.post.SimpleRegisteredPost
 import com.insanusmokrassar.postssystem.core.utils.pagination.PaginationResult
 import io.ktor.application.ApplicationCall
 import io.ktor.http.ContentType
@@ -15,8 +15,8 @@ import kotlinx.serialization.internal.NullableSerializer
 import kotlinx.serialization.json.Json
 
 
-internal val postsSerializer = ArrayListSerializer(SimplePost.serializer())
-internal val paginationResultSerializer = PaginationResult.serializer(SimplePost.serializer())
+internal val postsSerializer = ArrayListSerializer(SimpleRegisteredPost.serializer())
+internal val paginationResultSerializer = PaginationResult.serializer(SimpleRegisteredPost.serializer())
 
 internal val List<Post>.asSimplePostList
     get() = map { post ->
@@ -25,8 +25,8 @@ internal val List<Post>.asSimplePostList
 
 internal val Post.asSimplePost
     get() = when (this) {
-        is SimplePost -> this
-        else -> SimplePost(id, content, meta)
+        is SimpleRegisteredPost -> this
+        else -> SimpleRegisteredPost(id, content, meta)
     }
 
 @InternalSerializationApi
diff --git a/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/ReadModules.kt b/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/ReadModules.kt
index 326ac614..5d1498cd 100644
--- a/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/ReadModules.kt
+++ b/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/ReadModules.kt
@@ -8,17 +8,10 @@ import com.insanusmokrassar.postssystem.core.post.*
 import com.insanusmokrassar.postssystem.core.utils.pagination.PaginationRequest
 import com.insanusmokrassar.postssystem.core.utils.pagination.PaginationResult
 import io.ktor.application.*
-import io.ktor.features.ContentNegotiation
-import io.ktor.http.ContentType
-import io.ktor.http.HttpStatusCode
 import io.ktor.request.receiveOrNull
-import io.ktor.response.respond
-import io.ktor.response.respondText
 import io.ktor.routing.Route
 import io.ktor.routing.post
-import io.ktor.serialization.serialization
 import kotlinx.serialization.InternalSerializationApi
-import kotlinx.serialization.json.Json
 import org.joda.time.DateTime
 
 @InternalSerializationApi
@@ -26,7 +19,7 @@ fun Route.includePostsCoreReadModules(readPostsAPI: ReadPostsAPI) {
     post(getPostByIdAddress) {
         call.receiveOrNull<PostId>() ?.also { id ->
             val post = readPostsAPI.getPostById(id)
-            call.answer(SimplePost.serializer(), post ?.asSimplePost)
+            call.answer(SimpleRegisteredPost.serializer(), post ?.asSimplePost)
         } ?: call.answerBadRequest("Id of post")
     }
     post(getPostsByContentIdAddress) {
diff --git a/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/WriteModules.kt b/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/WriteModules.kt
index df93f7bf..975e11de 100644
--- a/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/WriteModules.kt
+++ b/ServerPart/src/main/kotlin/com/insanusmokrassar/postssystem/core/server/WriteModules.kt
@@ -5,14 +5,10 @@ import com.insanusmokrassar.postssystem.core.clientserver.common.*
 import com.insanusmokrassar.postssystem.core.clientserver.common.models.UpdatePostRequest
 import com.insanusmokrassar.postssystem.core.post.*
 import io.ktor.application.*
-import io.ktor.features.ContentNegotiation
-import io.ktor.http.ContentType
 import io.ktor.http.cio.websocket.Frame
 import io.ktor.request.receiveOrNull
 import io.ktor.routing.Route
 import io.ktor.routing.post
-import io.ktor.serialization.serialization
-import io.ktor.websocket.WebSockets
 import io.ktor.websocket.webSocket
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.collect
@@ -24,7 +20,7 @@ private inline fun Route.createWebsocket(path: String, flow: Flow<Post>) {
     webSocket("/$path") {
         flow.collect {
             val simplePost = it.asSimplePost
-            outgoing.send(Frame.Text(Json.plain.stringify(SimplePost.serializer(), simplePost)))
+            outgoing.send(Frame.Text(Json.plain.stringify(SimpleRegisteredPost.serializer(), simplePost)))
         }
     }
 }
@@ -41,7 +37,7 @@ fun Route.includePostsCoreWriteModules(
         call.receiveOrNull<PostContents>() ?.also { contents ->
             val post = writePostsAPI.createPost(contents)
 
-            call.answer(SimplePost.serializer(), post ?.asSimplePost)
+            call.answer(SimpleRegisteredPost.serializer(), post ?.asSimplePost)
         } ?: call.answerBadRequest("Contents (List of Content)")
     }