Merge pull request #19588 from taosdata/docs-cloud-ug

change data sharing to data subscription

docs/en/01-index.md

@@ -17,7 +17,7 @@ This is the documentation structure for TDengine Cloud.
 
 5. The [Visualization](./visual) section shows you how you can visualize the data that you store in TDengine, as well as how you can visualize and monitor the status of your TDengine Cloud instance(s) and databases.
 
-6. [Data Sharing](./data-sharing) is an advanced and useful feature of TDengine Cloud. In this section, we provide an easy way to share your data in the TDengine Cloud to others through only simple click operations.
+6. [Data Subscription](./data-subscription) is an advanced and useful feature of TDengine. It is similar to asynchronous publish/subscribe where a message published to a topic is immediately received by all subscribers to that topic. TDengine Subscriptions allow you to create event driven applications without having to install an external pub/sub messaging system. In the TDengien Cloud, we provide an easy way to create topic and share your topic in the TDengine Cloud to others through only simple click operations.
 
 7. [Stream Processing](./stream) is another extremely useful feature of TDengine Cloud that obviates the need to install external stream processing systems like Kafka or Flink. TDengine's Stream Processing feature allows you to process incoming data streams in real time and push data to tables based on rules that you can define easily.  
 

docs/en/02-intro.md

@@ -19,12 +19,13 @@ The major features are listed below:
    - Supports standard [SQL](../data-out/query-data/), including nested query.
    - Supports exporting data via tool [taosDump](../data-out/taosdump/).
    - Supports writing data to [Prometheus](../data-out/prometheus/).
+   - Supports exporting data via [data subscription](../data-subscription/).
 3. Data Explorer: browse through databases and even run SQL queries once you login.
 4. Visualization:
    - Supports [Grafana](../visual/grafana/)
    - Supports Google data studio (to be released soon)
    - Supports Grafana cloud (to be released soon)
-5. [Data Sharing](../data-sharing/):  sharing the topics with other users or user groups through simple operations in TDengine Cloud.
+5. [Data Subscription](../data-subscription/):  Application can subscribe a table or a set of tables. API is the same as Kafka, but you can specify filter conditions and you can share the topic with other users and user groups in TDengien Cloud.
 6. [Stream Processing](../stream/): Not only is the continuous query is supported, but TDengine also supports event driven stream processing, so Flink or Spark is not needed for time-series data processing.
 7. Enterprise
    - Supports backuping data everyday.

docs/en/09-data-out/index.md

@@ -4,4 +4,4 @@ title: Get Data Out of TDengine
 description: A number of ways getting data out of TDengine.
 ---
 
-This chapter introduces how to get data out of TDengine cloud service. Besides normal query using SQL, users can use [data sharing](../data-sharing) which is provided by TDengine cloud service to share the data stored in TDengine to others. TDengine provides [connectors](../programming/connector) for application programmers to access the data stored in TDengine. TDengine also provides some tools, like [taosdump](../tools/taosdump), which is a tool provided by TDengine to dump the data stored in TDengine cloud service into files, and `taosX`, which is another tool to sync up the data in one TDengine cloud service into another. Furthermore, 3rd party tools, like prometheus, can also be used to write data into TDengine.
+This chapter introduces how to get data out of TDengine cloud service. Besides normal query using SQL, users can use [data subscripition](../data-subscription) which is provided by TDengine cloud service to do data subscription and share the data stored in TDengine to others. TDengine provides [connectors](../programming/connector) for application programmers to access the data stored in TDengine. TDengine also provides some tools, like [taosdump](../tools/taosdump), which is a tool provided by TDengine to dump the data stored in TDengine cloud service into files, and `taosX`, which is another tool to sync up the data in one TDengine cloud service into another. Furthermore, 3rd party tools, like prometheus, can also be used to write data into TDengine.

docs/en/11-data-sharing/index.md → docs/en/11-data-subscription/index.md

 ---
-sidebar_label: Data Sharing
-title: Data Sharing
-description: Using topics to share data from TDengine.
+sidebar_label: Data Subscription
+title: Data Subscription
+description: Using topics to do data subscription and share to others from TDengine.
 ---
 import Tabs from "@theme/Tabs";
 import TabItem from "@theme/TabItem";
 
+TDengine provides data subscription and consumption interfaces similar to message queue products. These interfaces make it easier for applications to obtain data written to TDengine either in real time and to process data in the order that events occurred. This simplifies your time-series data processing systems and reduces your costs because it is no longer necessary to deploy a message queue product such as Kafka.
+
+To use TDengine data subscription, you define topics like in Kafka. However, a topic in TDengine is based on query conditions for an existing supertable, table, or subtable - in other words, a SELECT statement. You can use SQL to filter data by tag, table name, column, or expression and then perform a scalar function or user-defined function on the data. Aggregate functions are not supported. This gives TDengine data subscription more flexibility than similar products. The granularity of data can be controlled on demand by applications, while filtering and preprocessing are handled by TDengine instead of the application layer. This implementation reduces the amount of data transmitted and the complexity of applications.
+
+By subscribing to a topic, a consumer can obtain the latest data in that topic in real time. Multiple consumers can be formed into a consumer group that consumes messages together. Consumer groups enable faster speed through multi-threaded, distributed data consumption. Note that consumers in different groups that are subscribed to the same topic do not consume messages together. A single consumer can subscribe to multiple topics. If the data in a supertable is sharded across multiple vnodes, consumer groups can consume it much more efficiently than single consumers. TDengine also includes an acknowledgement mechanism that ensures at-least-once delivery in complicated environments where machines may crash or restart.
+
 The topic introduces how to share data from TDengine instance through the access control management of TDengine Cloud and the subscription interfaces of each supported connectors. The data owner first creates the topic through the topic wizard. Then adds the users or user groups which he wants to share the data with to the subscribers of the topic. The subscriber of the topic can get the details about how to access the shared data from TDengine in the data subscription way. In this document we will briefly explain these main steps of data sharing.
 
 ## Create Topic