apilloud commented on code in PR #24962:
URL: https://github.com/apache/beam/pull/24962#discussion_r1072943926


##########
website/www/site/content/en/documentation/io/io-standards.md:
##########
@@ -0,0 +1,1452 @@
+---
+title: "IO Standards"
+---
+<!--
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+# I/O Standards
+
+## Overview
+
+This Apache Beam I/O Standards document lays out the prescriptive guidance for 
1P/3P developers developing an Apache Beam I/O connector. These guidelines aim 
to create best practices encompassing documentation, development and testing in 
a simple and concise manner.
+
+
+### What are built-in I/O Connectors?
+
+An I/O connector (I/O) living in the Apache Beam Github repository is known as 
a **Built-in I/O connector**. Built-in I/O’s have their [integration 
tests](#integration-tests) and performance tests routinely run by the Google 
Cloud Dataflow Team using the Dataflow Runner and metrics published publicly 
for [reference](#dashboard). Otherwise, the following guidelines will apply to 
both unless explicitly stated.
+
+
+# Guidance
+
+
+## Documentation
+
+This section lays out the superset of all documentation that is expected to be 
made available with an I/O. The Apache Beam documentation referenced throughout 
this section can be found [here](https://beam.apache.org/documentation/). And 
generally a good example to follow would be the built-in I/O, [Snowflake 
I/O](https://beam.apache.org/documentation/io/built-in/snowflake/).
+
+
+### Built-in I/O
+
+<div class="table-container-wrapper">
+<table class="table table-bordered table-io-standards">
+   <tr>
+      <td>
+         <p>Provided code docs for the relevant language of the I/O. This 
should also have links to any external sources of information within the Apache 
Beam site or external documentation location.
+         <p>Examples:
+         <ul>
+            <li><a 
href="https://beam.apache.org/releases/javadoc/current/overview-summary.html";>Java
 doc</a>
+            <li><a 
href="https://beam.apache.org/releases/pydoc/current/";>Python doc</a>
+            <li><a 
href="https://pkg.go.dev/github.com/apache/beam/sdks/v2/go/pkg/beam";>Go doc</a>
+         </ul>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Add a new page under <strong>I/O connector guides</strong> that 
covers specific tips and configurations. The following shows those for <a 
href="https://beam.apache.org/documentation/io/built-in/parquet/";>Parquet</a>, 
<a href="https://beam.apache.org/documentation/io/built-in/hadoop/";>Hadoop</a> 
and others.
+         <p>Examples:
+         <p><img src="/images/io-standards/io-connector-guides-screenshot.png" 
width="" alt="I/O connector guides screenshot" title="I/O connector guides 
screenshot"></img>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Formatting of the section headers in your Javadoc/Pythondoc should 
be consistent throughout such that programmatic information extraction for 
other pages can be enabled in the future.
+         <p>Example <strong>subset</strong> of sections to include in your 
page in order:
+         <ol>
+            <li>Before you start
+            <li>{Connector}IO basics
+            <li>Supported Features
+               <ol>
+                  <li>Relational
+                  </li>
+               </ol>
+            <li>Authentication
+            <li>Reading from {Connector}
+            <li>Writing to {Connector}
+            <li><a href="#unit-tests">Resource scalability</a>

Review Comment:
   This link is odd. Why does `Resource scalability` link to `#unit-tests`? 
Should the rest be links too?



##########
website/www/site/content/en/documentation/io/io-standards.md:
##########
@@ -0,0 +1,1452 @@
+---
+title: "IO Standards"
+---
+<!--
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+# I/O Standards
+
+## Overview
+
+This Apache Beam I/O Standards document lays out the prescriptive guidance for 
1P/3P developers developing an Apache Beam I/O connector. These guidelines aim 
to create best practices encompassing documentation, development and testing in 
a simple and concise manner.
+
+
+### What are built-in I/O Connectors?
+
+An I/O connector (I/O) living in the Apache Beam Github repository is known as 
a **Built-in I/O connector**. Built-in I/O’s have their [integration 
tests](#integration-tests) and performance tests routinely run by the Google 
Cloud Dataflow Team using the Dataflow Runner and metrics published publicly 
for [reference](#dashboard). Otherwise, the following guidelines will apply to 
both unless explicitly stated.
+
+
+# Guidance
+
+
+## Documentation
+
+This section lays out the superset of all documentation that is expected to be 
made available with an I/O. The Apache Beam documentation referenced throughout 
this section can be found [here](https://beam.apache.org/documentation/). And 
generally a good example to follow would be the built-in I/O, [Snowflake 
I/O](https://beam.apache.org/documentation/io/built-in/snowflake/).

Review Comment:
   nit: Internal links should be relative. Drop https://beam.apache.org



##########
website/www/site/content/en/documentation/io/io-standards.md:
##########
@@ -0,0 +1,1452 @@
+---
+title: "IO Standards"
+---
+<!--
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+# I/O Standards
+
+## Overview
+
+This Apache Beam I/O Standards document lays out the prescriptive guidance for 
1P/3P developers developing an Apache Beam I/O connector. These guidelines aim 
to create best practices encompassing documentation, development and testing in 
a simple and concise manner.
+
+
+### What are built-in I/O Connectors?
+
+An I/O connector (I/O) living in the Apache Beam Github repository is known as 
a **Built-in I/O connector**. Built-in I/O’s have their [integration 
tests](#integration-tests) and performance tests routinely run by the Google 
Cloud Dataflow Team using the Dataflow Runner and metrics published publicly 
for [reference](#dashboard). Otherwise, the following guidelines will apply to 
both unless explicitly stated.
+
+
+# Guidance
+
+
+## Documentation
+
+This section lays out the superset of all documentation that is expected to be 
made available with an I/O. The Apache Beam documentation referenced throughout 
this section can be found [here](https://beam.apache.org/documentation/). And 
generally a good example to follow would be the built-in I/O, [Snowflake 
I/O](https://beam.apache.org/documentation/io/built-in/snowflake/).
+
+
+### Built-in I/O
+
+<div class="table-container-wrapper">
+<table class="table table-bordered table-io-standards">
+   <tr>
+      <td>
+         <p>Provided code docs for the relevant language of the I/O. This 
should also have links to any external sources of information within the Apache 
Beam site or external documentation location.
+         <p>Examples:
+         <ul>
+            <li><a 
href="https://beam.apache.org/releases/javadoc/current/overview-summary.html";>Java
 doc</a>
+            <li><a 
href="https://beam.apache.org/releases/pydoc/current/";>Python doc</a>
+            <li><a 
href="https://pkg.go.dev/github.com/apache/beam/sdks/v2/go/pkg/beam";>Go doc</a>
+         </ul>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Add a new page under <strong>I/O connector guides</strong> that 
covers specific tips and configurations. The following shows those for <a 
href="https://beam.apache.org/documentation/io/built-in/parquet/";>Parquet</a>, 
<a href="https://beam.apache.org/documentation/io/built-in/hadoop/";>Hadoop</a> 
and others.
+         <p>Examples:
+         <p><img src="/images/io-standards/io-connector-guides-screenshot.png" 
width="" alt="I/O connector guides screenshot" title="I/O connector guides 
screenshot"></img>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Formatting of the section headers in your Javadoc/Pythondoc should 
be consistent throughout such that programmatic information extraction for 
other pages can be enabled in the future.
+         <p>Example <strong>subset</strong> of sections to include in your 
page in order:
+         <ol>
+            <li>Before you start
+            <li>{Connector}IO basics
+            <li>Supported Features
+               <ol>
+                  <li>Relational
+                  </li>
+               </ol>
+            <li>Authentication
+            <li>Reading from {Connector}
+            <li>Writing to {Connector}
+            <li><a href="#unit-tests">Resource scalability</a>
+            <li>Limitations
+            <li>Reporting an Issue
+            </li>
+         </ol>
+         <p>Example:
+         <p>The KafkaIO <a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/kafka/KafkaIO.html";>JavaDoc</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>I/O Connectors should include a note indicating <a 
href="https://2022.beamsummit.org/sessions/relational-beam/";>Relational 
Features</a> supported in their page under <strong>I/O connector 
guides</strong>.
+         <p>Relational Features are concepts that can help improve efficiency 
and can optionally be implemented by an I/O Connector. Using end user supplied 
pipeline configuration (<a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/schemas/io/SchemaIO.html";>SchemaIO</a>)
 and user query (<a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/schemas/FieldAccessDescriptor.html";>FieldAccessDescriptor</a>)
 data, relational theory is applied to derive improvements such as faster 
pipeline execution, lower operation costs and less data read/written.
+         <p>Example table:
+         <p><img 
src="/images/io-standards/io-supported-relational-features-table.png" width="" 
alt="Supported Relational Features" title="Supported Relational Features"></img>

Review Comment:
   Please make this text and not a table. Markdown tables might be a good 
choice, if not HTML tables work too.



##########
website/www/site/content/en/documentation/io/io-standards.md:
##########
@@ -0,0 +1,1452 @@
+---
+title: "IO Standards"
+---
+<!--
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+# I/O Standards
+
+## Overview
+
+This Apache Beam I/O Standards document lays out the prescriptive guidance for 
1P/3P developers developing an Apache Beam I/O connector. These guidelines aim 
to create best practices encompassing documentation, development and testing in 
a simple and concise manner.
+
+
+### What are built-in I/O Connectors?
+
+An I/O connector (I/O) living in the Apache Beam Github repository is known as 
a **Built-in I/O connector**. Built-in I/O’s have their [integration 
tests](#integration-tests) and performance tests routinely run by the Google 
Cloud Dataflow Team using the Dataflow Runner and metrics published publicly 
for [reference](#dashboard). Otherwise, the following guidelines will apply to 
both unless explicitly stated.
+
+
+# Guidance
+
+
+## Documentation
+
+This section lays out the superset of all documentation that is expected to be 
made available with an I/O. The Apache Beam documentation referenced throughout 
this section can be found [here](https://beam.apache.org/documentation/). And 
generally a good example to follow would be the built-in I/O, [Snowflake 
I/O](https://beam.apache.org/documentation/io/built-in/snowflake/).
+
+
+### Built-in I/O
+
+<div class="table-container-wrapper">
+<table class="table table-bordered table-io-standards">
+   <tr>
+      <td>
+         <p>Provided code docs for the relevant language of the I/O. This 
should also have links to any external sources of information within the Apache 
Beam site or external documentation location.
+         <p>Examples:
+         <ul>
+            <li><a 
href="https://beam.apache.org/releases/javadoc/current/overview-summary.html";>Java
 doc</a>
+            <li><a 
href="https://beam.apache.org/releases/pydoc/current/";>Python doc</a>
+            <li><a 
href="https://pkg.go.dev/github.com/apache/beam/sdks/v2/go/pkg/beam";>Go doc</a>
+         </ul>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Add a new page under <strong>I/O connector guides</strong> that 
covers specific tips and configurations. The following shows those for <a 
href="https://beam.apache.org/documentation/io/built-in/parquet/";>Parquet</a>, 
<a href="https://beam.apache.org/documentation/io/built-in/hadoop/";>Hadoop</a> 
and others.
+         <p>Examples:
+         <p><img src="/images/io-standards/io-connector-guides-screenshot.png" 
width="" alt="I/O connector guides screenshot" title="I/O connector guides 
screenshot"></img>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Formatting of the section headers in your Javadoc/Pythondoc should 
be consistent throughout such that programmatic information extraction for 
other pages can be enabled in the future.
+         <p>Example <strong>subset</strong> of sections to include in your 
page in order:
+         <ol>
+            <li>Before you start
+            <li>{Connector}IO basics
+            <li>Supported Features
+               <ol>
+                  <li>Relational
+                  </li>
+               </ol>
+            <li>Authentication
+            <li>Reading from {Connector}
+            <li>Writing to {Connector}
+            <li><a href="#unit-tests">Resource scalability</a>
+            <li>Limitations
+            <li>Reporting an Issue
+            </li>
+         </ol>
+         <p>Example:
+         <p>The KafkaIO <a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/kafka/KafkaIO.html";>JavaDoc</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>I/O Connectors should include a note indicating <a 
href="https://2022.beamsummit.org/sessions/relational-beam/";>Relational 
Features</a> supported in their page under <strong>I/O connector 
guides</strong>.
+         <p>Relational Features are concepts that can help improve efficiency 
and can optionally be implemented by an I/O Connector. Using end user supplied 
pipeline configuration (<a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/schemas/io/SchemaIO.html";>SchemaIO</a>)
 and user query (<a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/schemas/FieldAccessDescriptor.html";>FieldAccessDescriptor</a>)
 data, relational theory is applied to derive improvements such as faster 
pipeline execution, lower operation costs and less data read/written.
+         <p>Example table:
+         <p><img 
src="/images/io-standards/io-supported-relational-features-table.png" width="" 
alt="Supported Relational Features" title="Supported Relational Features"></img>
+         <p>Example implementations:
+         <p>BigQueryIO <a 
href="https://github.com/apache/beam/blob/5bb13fa35b9bc36764895c57f23d3890f0f1b567/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.java#L1813";>Column
 Pruning</a> via ProjectionPushdown to return only necessary columns indicated 
by an end user's query. This is achieved using BigQuery DirectRead API.
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Add a page under <strong>Common pipeline patterns</strong>, if 
necessary, outlining common usage patterns involving your I/O.
+         <p><a 
href="https://beam.apache.org/documentation/patterns/bigqueryio/";>https://beam.apache.org/documentation/patterns/bigqueryio/</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Update <strong>I/O Connectors</strong> with your I/O’s information
+         <p>Example:
+         <p><a 
href="https://beam.apache.org/documentation/io/connectors/#built-in-io-connectors";>https://beam.apache.org/documentation/io/connectors/#built-in-io-connectors</a>
+         <p><img src="/images/io-standards/io-supported-via-screenshot.png" 
width="" alt="alt_text" title="image_tooltip">
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Provide setup steps to use the I/O, under a <strong>Before you 
start Header</strong>
+         <p>Example:
+         <p><a 
href="https://beam.apache.org/documentation/io/built-in/parquet/#before-you-start";>https://beam.apache.org/documentation/io/built-in/parquet/#before-you-start</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Include a canonical read/write code snippet after the initial 
description for each supported language. The below example shows Hadoop with 
examples for Java.
+         <p>Example:
+         <p><a 
href="https://beam.apache.org/documentation/io/built-in/hadoop/#reading-using-hadoopformatio";>https://beam.apache.org/documentation/io/built-in/hadoop/#reading-using-hadoopformation</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Indicate how timestamps for elements are assigned. This includes 
batch sources to allow for future I/Os which may provide more useful 
information than current_time().
+         <p>Example:
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Indicate how timestamps are advanced; for Batch sources this will 
be marked as n/a in most cases.
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Outline any temporary resources (for example, files) that the 
connector will create.
+         <p>Example:
+         <p>BigQuery batch loads first create a temp GCS location
+         <p><a 
href="https://github.com/apache/beam/blob/master/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.java#L455";>https://github.com/apache/beam/blob/master/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.java#L455</a>
+      </td>
+  </tr>
+  <tr>
+      <td>
+         <p>Provide, under an <strong>Authentication</strong> subheader, how 
to acquire partner authorization material to securely access the source/sink.
+         <p>Example:
+         <p><a 
href="https://beam.apache.org/documentation/io/built-in/snowflake/#authentication";>https://beam.apache.org/documentation/io/built-in/snowflake/#authentication</a>
+         <p>Here BigQuery names it permissions but the topic covers 
similarities
+         <p><a 
href="https://beam.apache.org/releases/javadoc/2.1.0/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.html";>https://beam.apache.org/releases/javadoc/2.1.0/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.html</a>
+      </td>
+  </tr>
+  <tr>
+      <td>
+         <p>I/Os should provide links to the Source/Sink documentation within 
<strong>Before you start Header</strong>
+         <p>Example:
+         <p><a 
href="https://beam.apache.org/documentation/io/built-in/snowflake/";>https://beam.apache.org/documentation/io/built-in/snowflake/</a>
+      </td>
+  </tr>
+  <tr>
+      <td>
+         <p>Indicate if there is native or X-language support in each language 
with a link to the docs.
+         <p>Example:
+         <p>Kinesis I/O has a native implementation of java and X-language 
support for python but no support for Golang.
+      </td>
+  </tr>
+  <tr>
+   <td>
+      <p>Indicate known limitations under a <strong>Limitations</strong> 
header. If the limitation has a tracking issue, please link it inline.
+      <p>Example:
+      <p><a 
href="https://beam.apache.org/documentation/io/built-in/snowflake/#limitations";>https://beam.apache.org/documentation/io/built-in/snowflake/#limitations</a>
+   </td>
+  </tr>
+</table>
+</div>
+
+
+
+### I/O (not built-in)
+
+Custom I/Os are not included in the Apache Beam Github repository. Some 
examples would be 
[Solace](https://github.com/SolaceProducts/solace-apache-beam)IO.
+
+<div class="table-container-wrapper">
+<table class="table table-bordered table-connectors">
+   <tr>
+      <td>
+         <p>Update I/O connectors with your I/O information
+         <p>Example:
+         <p><a 
href="https://beam.apache.org/documentation/io/connectors/#other-io-connectors-for-apache-beam";>https://beam.apache.org/documentation/io/built-in/snowflake/#limitations</a>
+      </td>
+   </tr>
+</table>
+</div>
+
+## Development
+
+This section outlines API Syntax, Semantics and Feature Adoption 
recommendations for new and existing Apache Beam I/O Connectors.
+
+Development guidelines are written with the following principles in mind:
+
+
+
+* Consistency makes an API easier to learn
+    * If there are multiple ways of doing something, we should strive to be 
consistent first
+* With a couple minutes of studying documentation, users should be able to 
pick up most I/O connectors
+* The design of a new I/O should consider the possibility of evolution
+* Transforms should integrate well with other Beam utilities
+
+
+### All SDKs
+
+
+#### Pipeline Configuration / Execution / Streaming / Windowing semantics 
guidelines
+
+<div class="table-container-wrapper">
+<table class="table table-bordered table-io-standards">
+   <tr>
+      <th>
+         <p>Topic
+      </th>
+      <th>
+         <p>Semantics
+      </th>
+   </tr>
+   <tr>
+      <td>
+         <p>Pipeline Options
+      </td>
+      <td>
+         <p>An I/O should rarely rely on a PipelineOptions subclass to tune 
internal parameters.
+         <p>A connector-related pipeline options class should:
+         <ul>
+            <li>Document clearly, for each option, the effect it has and why 
one may modify it.
+            <li>Option names must be namespaced to avoid collisions
+            <li>Class Name: {Connector}Options
+            <li>Method names: .set{Connector}{Option}, get{Connector}{Option}
+            </li>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Source Windowing
+      </td>
+      <td>
+         <p>A source must return elements in the GlobalWindow unless 
explicitly parameterized in the API by the user.
+         <p>Allowable Non-global-window patterns:
+         <ul>
+            <li>ReadFromIO(window_by=...)
+            <li>ReadFromIO.IntoFixedWindows(...)
+            <li>ReadFromIO(apply_windowing=True/False) (e.g. <a 
href="https://beam.apache.org/releases/pydoc/current/apache_beam.transforms.periodicsequence.html#apache_beam.transforms.periodicsequence.PeriodicImpulse";>PeriodicImpulse</a>)
+            <li>IO.read().withWindowing(...)
+            <li>IO.read().windowBy(...)
+            <li>IO.read().withFixedWindows(...)
+            </li>
+         </ul>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Sink Windowing
+      </td>
+      <td>
+         <p>A sink should be Window agnostic and handle elements sent with any 
Windowing methodexpect elements to be sent to it in the Global Window, unless 
explicitly parameterized or expressed in its API.
+         <p>A sink may change the windowing of a PCollection internally 
however it needs, however, the metadata that it returns as part of its Result 
object must be:
+         <ul>
+            <li>In the same window, unless explicitly declared in the API
+            <li>With accurate timestamps
+            <li><strong>It may</strong> also return metadata with information 
about windowing (e.g. a BigQuery job may have a timestamp, but also a window 
associated with it).
+         </ul>
+         <p>Allowable non-global-window patterns:
+         <ul>
+            <li>WriteToIO(triggering_frequency=...) - e.g. <a 
href="https://beam.apache.org/releases/pydoc/current/apache_beam.io.gcp.bigquery.html#apache_beam.io.gcp.bigquery.WriteToBigQuery";>WriteToBigQuery</a>
 (This only sets the windowing within the transform - input data is still in 
the Global Window).
+            <li>WriteBatchesToIO(...)
+            <li>WriteWindowsToIO(...)
+            </li>
+         </ul>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Throttling
+      </td>
+      <td>
+         <p>A streaming sink (or any transform accessing an external service) 
may implement throttling of its requests to prevent from overloading the 
external service.
+         <p>TODO: Beam should expose throttling utilities (<a 
href="https://github.com/apache/beam/issues/24743";>Tracking Issue</a>):
+         <ul>
+            <li>Per-key fixed throttling
+            <li>Adaptive throttling with sink-reported backpressure
+            <li>Ramp-up throttling from a start point
+            </li>
+         </ul>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>Error handling
+      </td>
+      <td>
+         <p>TODO: <a 
href="https://github.com/apache/beam/issues/24742";>Tracking Issue</a>
+      </td>
+   </tr>
+</table>
+</div>
+
+
+
+### Java
+
+
+#### General
+
+<div class="table-container-wrapper">
+<table class="table table-bordered table-io-standards">
+   <tr>
+      <td>
+         <p>The primary class used in working with the connector should be 
named <strong>{connector}IO</strong>
+         <p>Example:
+         <p>The BigQuery I/O is 
<strong>org.apache.beam.sdk.io.bigquery.BigQueryIO</strong>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>The class should be placed in the package 
<strong>org.apache.beam.sdk.io.{connector}</strong>
+         <p>Example:
+         <p>The BigQueryIO belongs in the java package <a 
href="https://github.com/apache/beam/blob/master/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.java";>org.apache.beam.sdk.io.bigquery</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>The unit/integration/performance tests should live under the 
package <strong>org.apache.beam.sdk.io.{connector}.testing</strong>. This will 
cause the various tests to work with the standard user-facing interfaces of the 
connector.
+         <p>Unit tests should reside in the same package (i.e. 
<strong>org.apache.beam.sdk.io.{connector}</strong>), as they may often test 
internals of the connector.
+         <p>The BigQueryIO belongs in the java package <a 
href="https://github.com/apache/beam/blob/master/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.java";>org.apache.beam.sdk.io.bigquery</a>
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>An I/O transform should avoid receiving user lambdas to map 
elements from a user type to a connector-specific type. Instead, they should 
interface with a connector-specific data type (with schema information when 
possible).
+         <p>When necessary, then an I/O transform should receive a type 
parameter that specifies the input type (for sinks) or output type (for 
sources) of the transform.
+         <p>An I/O transform may not have a type parameter <strong>only if it 
is certain that its output type will not change</strong> (e.g. <a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/FileIO.MatchAll.html";>FileIO.MatchAll</a>
 and other <a 
href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/FileIO.html";>FileIO
 transforms</a>).
+      </td>
+   </tr>
+   <tr>
+      <td>
+         <p>As part of the API of an I/O, it is highly discouraged to directly 
expose third-party libraries in the public API of a Beam API or connector.
+         <ul>
+            <li>It reduces Apache Beam’s compatibility guarantees - Changes to 
third-party libraries can/will directly break existing user’s pipelines.
+            <li>It makes code maintainability hard - If libraries are directly 
exposed at API level, a dependency change will require multiple changes 
throughout the I/O implementation code
+            <li>It forces third-party dependencies onto end users
+            </li>
+         </ul>
+         <p>Instead, we highly recommend exposing Beam-native interfaces and 
an adaptor be implemented to translate.
+         <p>If you believe that the library in question is extremely static in 
nature. Please note it in the I/O itself.
+         <p>As part of the API of an I/O, it is <strong>highly 
discouraged</strong> to expose third-party libraries in the public API of a 
Beam API or connector,. Instead, a Beam-native interface should be used and 
adapted into the third-library object.

Review Comment:
   This repeats the same thing again.



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