updated chat concepts

initial check-in

Author: vac0224

articles/communication-services/concepts/chat/concepts.md

@@ -37,20 +37,22 @@ Chat conversations happen within **chat threads**. Chat threads have the followi
 ### User access
 Azure Communication Services supports three levels of user access control, using the chat tokens. See [Identity and Tokens](../identity-model.md) for details. Participants don't have write-access to messages sent by other participants, which means only the message sender can update or delete their sent messages. If another participant tries to do that, they get an error. 
 
-### Chat Data 
+### Chat Data
+
 Azure Communication Services stores chat threads according to the [data retention policy](/purview/create-retention-policies) in effect when the thread is created. You can update the retention policy if needed during the retention time period you set. After you delete a chat thread (by policy or by a Delete API request), it can't be retrieved.
 
 [!INCLUDE [chat-retention-policy.md](../../includes/chat-retention-policy.md)]
 
 You can choose between indefinite thread retention, automatic deletion between 30 and 90 days via the retention policy on the [Create Chat Thread API](/rest/api/communication/chat/chat/create-chat-thread), or immediate deletion using the APIs [Delete Chat Message](/rest/api/communication/chat/chat-thread/delete-chat-message) or [Delete Chat Thread](/rest/api/communication/chat/chat/delete-chat-thread). 
 
-Any thread created before the new retention policy isn't affected unless you specifically change the policy for that thread. If you submit a support request for a deleted chat thread more than 30 days after the retention policy has deleted that thread, it can no longer be retrieved and no information about that thread is available. If needed, open a support ticket as quickly as possible within the 30 day window after you create a thread so we can assist you.
+Any thread created before the new retention policy isn't affected unless you specifically change the policy for that thread. If you submit a support request for a deleted chat thread more than 30 days after the retention policy deleted that thread, it can no longer be retrieved and no information about that thread is available. If needed, open a support ticket as quickly as possible within the 30 day window after you create a thread so we can assist you.
 
 Chat thread participants can use `ListMessages` to view message history for a particular thread. The `ListMessages` API can't return the history of a thread if the thread is deleted. Users that are removed from a chat thread are able to view previous message history but can't send or receive new messages. Accidentally deleted messages aren't recoverable by the system. To learn more about data being stored in Azure Communication Services chat service, refer to the [data residency and privacy page](../privacy.md). 
 
 For customers that use Virtual appointments, refer to our Teams Interoperability [user privacy](../interop/guest/privacy.md#chat-storage) for storage of chat messages in Teams meetings.
 
 ### Service limits
+
 - The maximum number of participants allowed in a chat thread is 250.
 - The maximum message size allowed is approximately 28 KB.
 - For chat threads with more than 20 participants, read receipts and typing indicator features aren't supported.
@@ -59,7 +61,7 @@ For customers that use Virtual appointments, refer to our Teams Interoperability
 - Moreover, in Teams Interop scenarios, there are the following limitations:
     - The Teams user's display name in typing indicator event is blank.
     - Read receipt isn't supported.
-    - Certain identities are not supported (i.e. [Bot users](/microsoftteams/platform/bots/what-are-bots), [Skype users](https://support.microsoft.com/en-us/office/use-skype-in-microsoft-teams-4382ea15-f963-413d-8982-491c1b9ae3bf), [non-enterprise users](https://support.microsoft.com/en-us/office/learn-more-about-subscriptions-for-microsoft-teams-free-1061bbd0-6d97-46a6-8ca0-21059be3eee3), etc.)
+    - Certain identities aren't supported, such as [Bot users](/microsoftteams/platform/bots/what-are-bots), [Skype users](https://support.microsoft.com/en-us/office/use-skype-in-microsoft-teams-4382ea15-f963-413d-8982-491c1b9ae3bf), [non-enterprise users](https://support.microsoft.com/en-us/office/learn-more-about-subscriptions-for-microsoft-teams-free-1061bbd0-6d97-46a6-8ca0-21059be3eee3), and similar.
 
 ## Chat architecture
 
@@ -90,13 +92,13 @@ System messages are generated when
 - a participant was added or removed 
 - the chat thread topic was updated.
 
-When you call `List Messages` or `Get Messages` on a chat thread, the result contains both kind of messages in chronological order. For user-generated messages, the message type can be set in `SendMessageOptions` when sending a message to chat thread. If no value is provided, Communication Services defaults to `text` type. Setting this value is important when sending HTML. When `html` is specified, Communication Services sanitizes the content to ensure that it's rendered safely on client devices.
+When you call `List Messages` or `Get Messages` on a chat thread, the result contains both kind of messages in chronological order. For user-generated messages, the message type can be set in `SendMessageOptions` when sending a message to chat thread. If no value is provided, Communication Services defaults to `text` type. Setting this value is important when sending HTML. When `html` is specified, Communication Services sanitizes the content to ensure that it rendered safely on client devices.
  - `text`: A plain text message composed and sent by a user as part of a chat thread. 
  - `html`: A formatted message using html, composed and sent by a user as part of chat thread. 
 
 Types of system messages: 
  - `participantAdded`: System message that indicates one or more participants are in the chat thread.
- - `participantRemoved`: System message that indicates a participant has been removed from the chat thread.
+ - `participantRemoved`: System message that indicates a participant is removed from the chat thread.
  - `topicUpdated`: System message that indicates the thread topic is updated.
 
 ## Real-time notifications
@@ -126,7 +128,7 @@ This feature lets server applications listen to events such as when a message is
 
 ## Push notifications 
 
-Android and iOS Chat SDKs support push notifications. To send push notifications for messages missed by your participants while they were away, connect a Notification Hub resource with Communication Services resource to send push notifications. Doing this notifies your application participants about incoming chats and messages when the mobile app is not running in the foreground.    
+Android and iOS Chat SDKs support push notifications. To send push notifications for messages missed by your participants while they were away, connect a Notification Hub resource with Communication Services resource to send push notifications. Doing this notifies your application participants about incoming chats and messages when the mobile app isn't running in the foreground.    
 
 IOS and Android SDK support the below event:
 - `chatMessageReceived` - when a participant sends a new message to a chat thread.     

articles/communication-services/concepts/privacy.md

@@ -38,8 +38,6 @@ The list of geographies you can choose from includes:
 - United Kingdom
 - United States
 
-
-
 ## Data collection
 
 Azure Communication Services only collects diagnostic data required to deliver the service. 
@@ -77,7 +75,15 @@ Azure Communication Services maintains a directory of phone numbers associated w
 
 ### Chat
 
-Azure Communication Services stores chat messages indefinitely till they are deleted. Chat thread participants can use ListMessages to view message history for a particular thread. Users that are removed from a chat thread are able to view previous message history but cannot send or receive new messages. Accidentally deleted messages are not recoverable by the system.
+Azure Communication Services stores chat threads according to the [data retention policy](/purview/create-retention-policies) in effect when the thread is created. You can update the retention policy if needed during the retention time period you set. After you delete a chat thread (by policy or by a Delete API request), it can't be retrieved.
+
+[!INCLUDE [chat-retention-policy.md](../../includes/chat-retention-policy.md)]
+
+You can choose between indefinite thread retention, automatic deletion between 30 and 90 days via the retention policy on the [Create Chat Thread API](/rest/api/communication/chat/chat/create-chat-thread), or immediate deletion using the APIs [Delete Chat Message](/rest/api/communication/chat/chat-thread/delete-chat-message) or [Delete Chat Thread](/rest/api/communication/chat/chat/delete-chat-thread). 
+
+Any thread created before the new retention policy isn't affected unless you specifically change the policy for that thread. If you submit a support request for a deleted chat thread more than 30 days after the retention policy has deleted that thread, it can no longer be retrieved and no information about that thread is available. If needed, open a support ticket as quickly as possible within the 30 day window after you create a thread so we can assist you.
+
+Chat thread participants can use `ListMessages` to view message history for a particular thread. The `ListMessages` API can't return the history of a thread if the thread is deleted. Users that are removed from a chat thread are able to view previous message history but can't send or receive new messages. Accidentally deleted messages aren't recoverable by the system.
 
 Use [Chat APIs](/rest/api/communication/chat/chatthread) to get, list, update, and delete messages.