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+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE chapter SYSTEM "chapter.dtd">
+
+<chapter>
+ <header>
+ <copyright>
+ <year>2018</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ 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.
+
+ </legalnotice>
+
+ <title>Support, Compatibility, Deprecations, and Removal</title>
+ <prepared></prepared>
+ <responsible></responsible>
+ <docno></docno>
+ <approved></approved>
+ <checked></checked>
+ <date>2018-05-21</date>
+ <rev></rev>
+ <file>misc.xml</file>
+ </header>
+
+ <section>
+ <marker id="supported_releases"/>
+ <title>Supported Releases</title>
+ <p>
+ In general, bugs are only fixed on the latest
+ <seealso marker="versions#releases_and_patches">release</seealso>,
+ and new features are introduced in the upcoming release that is
+ under development. However, when we, due to internal reasons, fix
+ bugs on older releases, these will be available and announced as well.
+ </p>
+ <p>
+ Due to the above, pull requests are only accepted on the
+ <c>maint</c> and the <c>master</c> branches in our
+ <url href="https://github.com/erlang/otp">git repository</url>.
+ The <c>maint</c> branch contains changes planned for the next
+ <seealso marker="versions#releases_and_patches">maintenance patch package</seealso>
+ on the latest OTP release and the <c>master</c> branch contain
+ changes planned for the upcoming OTP release.
+ </p>
+ </section>
+
+ <section>
+ <marker id="compatibility"/>
+ <title>Compatibility</title>
+ <p>
+ We always strive to remain as compatible as possible
+ even in the cases where we give no compatibility guarantees.
+ </p>
+ <p>
+ Different parts of the system will be handled differently
+ regarding compatibility. The following items describe how
+ different parts of the system are handled.
+ </p>
+ <taglist>
+ <tag>Erlang Distribution</tag>
+ <item>
+ <p>
+ Erlang nodes can communicate across at least
+ two preceding and two subsequent releases.
+ </p>
+ </item>
+ <tag>Compiled BEAM Code, NIF Libraries and Drivers</tag>
+ <item>
+ <p>
+ Compiled code can be loaded on at least two
+ subsequent releases.
+ </p>
+ <p>
+ Loading on previous releases is <em>not</em> supported.
+ </p>
+ </item>
+ <tag>Compiled HiPE Code</tag>
+ <item>
+ <p>
+ Compiled HiPE code can be loaded on the exact same build
+ of ERTS that was used when compiling the code. It might
+ however work on other builds, the emulator verifies
+ checksums in order to determine if it can load the code
+ or not. Note that HiPE has some limitations. For more
+ information see the documentation of the
+ <seealso marker="hipe:HiPE_app">HiPE</seealso> application.
+ </p>
+ </item>
+ <tag>APIs</tag>
+ <item>
+ <p>Compatible between releases.</p>
+ </item>
+ <tag>Compiler Warnings</tag>
+ <item>
+ <p>New warnings may be issued between releases.</p>
+ </item>
+ <tag>Command Line Arguments</tag>
+ <item>
+ <p>Incompatible changes may occur between releases.</p>
+ </item>
+ <tag>OTP Build Procedures</tag>
+ <item><p>Incompatible changes may occur between releases.</p></item>
+ </taglist>
+ <p>
+ Under certain circumstances incompatible changes might be
+ introduced even in parts of the system that should be compatible
+ between releases. Things that might trigger incompatible changes
+ like this are:
+ </p>
+ <taglist>
+ <tag>Security Issues</tag>
+ <item>
+ <p>
+ It might be necessary to introduce incompatible changes
+ in order to solve a security issue. This kind of
+ incompatibility might occur in a patch.
+ </p>
+ </item>
+ <tag>Bug Fixes</tag>
+ <item>
+ <p>
+ We will not be bug-compatible. A bug fix might introduce
+ incompatible changes. This kind of incompatibility
+ might occur in a patch.
+ </p>
+ </item>
+ <tag>Severe Previous Design Issues</tag>
+ <item>
+ <p>
+ Some parts of OTP were designed a very long time ago and
+ did not necessarily take today's computing environments into
+ account. In some cases the consequences of those design
+ decisions are too severe. This may be performance wise,
+ scalability wise, etc. If we deem the consequences too
+ severe, we might introduce incompatible changes. This kind
+ of incompatibility will not be introduced in a patch, but
+ instead in the next release.
+ </p>
+ </item>
+ </taglist>
+ <p>
+ Peripheral, trace, and debug functionality is at greater
+ risk of being changed in an incompatible way than functionality
+ in the language itself and core libraries used during operation.
+ </p>
+ </section>
+
+ <section>
+ <marker id="deprecation"/>
+ <title>Deprecation</title>
+ <p>
+ Functionality is deprecated when new functionality is
+ introduced that is preferred to be used instead of the
+ old functionality that is being deprecated. The deprecation
+ does <em>not</em> imply removal of the functionality unless
+ an upcoming removal is explicitly stated in the deprecation.
+ </p>
+ <p>
+ Deprecated functionality will be documented as deprecated, and
+ compiler warnings will be issued, when appropriate, as
+ early as possible. That is, the new preferred functionality
+ will appear at the same time as the deprecation is issued.
+ A new deprecation will at least be announced in a release
+ note and the documentation.
+ </p>
+ </section>
+
+ <section>
+ <marker id="removal"/>
+ <title>Removal</title>
+ <p>
+ Legacy solutions may eventually need to be removed. In such
+ cases, they will be phased out on a long enough time period
+ to give users the time to adapt. Before removal of
+ functionality it will be deprecated at least during one
+ release with an explicit announcement about
+ the upcoming removal. A new deprecation will at least be
+ announced in a release note and the documentation.
+ </p>
+ <p>
+ Peripheral, trace, and debug functionality is at greater
+ risk of removal than functionality in the language itself
+ and core libraries used during operation.
+ </p>
+ </section>
+
+</chapter>
+