Document the ASDF release cycle and supported dependencies

CHANGES.rst

@@ -8,6 +8,8 @@ The ASDF Standard is at v1.6.0
   may undergo breaking changes but are likely to be included as stable
   features (without this warning) in a future version of ASDF [#1295]
 - Add AsdfDeprecationWarning to AsdfFile.blocks [#1336]
+- Document policy for ASDF release cycle including when support for ASDF versions
+  end. Also document dependency support policy. [#1323]
 
 2.14.3 (2022-12-15)
 -------------------

docs/asdf/release_and_support.rst

@@ -0,0 +1,102 @@
+.. currentmodule:: asdf
+
+.. _release_and_support:
+
+*************************************************
+Release Cycle and Major Dependency Support Policy
+*************************************************
+
+This document describes a general plan for releasing the ASDF library, along with
+how long we intend to support each release. Moreover, it also describes our policy
+for how long we plan to support versions of CPython and NumPy. Note that this is
+a living document, and may be updated at any time.
+
+.. _release_cycle:
+
+Release Cycle
+=============
+
+As ASDF is still under active development, it will continue to be developed on a
+rolling release cycle. This means that ASDF will not have a fixed release
+schedule, but rather will be released as needed.
+
+However, we do intend to create and maintain designated "long-term support" (LTS)
+branches for at least major version of ASDF in a similar way as what is described
+for ``astropy`` in `APE 2 <https://github.com/astropy/astropy-APEs/blob/main/APE2.rst>`_.
+This means that for every new major version of ASDF, say version ``a.0`` we will
+designate and maintain ``a.0.x`` as the LTS branch of ASDF for at least one year.
+During this time we will try to ensure that the LTS branch receives bugfixes and
+has regular releases. After one year, we may decide to designate a new LTS branch
+for ASDF if no new major versions of ASDF have been released; otherwise, we will
+cease to maintain the old LTS branch in favor of the newer one(s). Aside from the
+LTS version(s), we will also maintain a rolling current version of ASDF. This support
+for these rolling versions will end when the next non-LTS version of ASDF is released.
+
+.. note::
+
+    Since this policy has not yet been implemented, we have not yet formally declared
+    an LTS version for ASDF. Our plan is to declare ``2.15`` as an LTS version when it
+    is released and move forward to actively working on ASDF ``3.0`` as our main development.
+    Once ``3.0`` is released, it will also become a second LTS version of ASDF and we
+    will continue to release bugfixes for ASDF ``2.15`` and ``3.0`` for at least one
+    year past their release dates.
+
+.. _dependency_support_policy:
+
+Dependency Support Policy
+=========================
+
+ASDF primarily depends on CPython and NumPy. As a scientific Python library, we
+have chosen to abide by the policy laid out in
+`NEP 29 <https://numpy.org/neps/nep-0029-deprecation_policy.html>`_.
+The following table summarizes this policy:
+
+============ ====== =====
+Date         Python NumPy
+------------ ------ -----
+Jan 31, 2023 3.8+   1.21+
+Apr 14, 2023 3.9+   1.21+
+Jun 23, 2023 3.9+   1.22+
+Jan 01, 2024 3.9+   1.23+
+Apr 05, 2024 3.10+  1.23+
+Jun 22, 2024 3.10+  1.24+
+Dec 18, 2024 3.10+  1.25+
+Apr 04, 2025 3.11+  1.25+
+Apr 24, 2026 3.12+  1.25+
+============ ====== =====
+
+.. _drop_schedule:
+
+CPython and NumPy Drop Schedule
+-------------------------------
+
+::
+
+  On Jan 31, 2023 drop support for NumPy 1.20 (initially released on Jan 31, 2021)
+  On Apr 14, 2023 drop support for Python 3.8 (initially released on Oct 14, 2019)
+  On Jun 23, 2023 drop support for NumPy 1.21 (initially released on Jun 22, 2021)
+  On Jan 01, 2024 drop support for NumPy 1.22 (initially released on Dec 31, 2021)
+  On Apr 05, 2024 drop support for Python 3.9 (initially released on Oct 05, 2020)
+  On Jun 22, 2024 drop support for NumPy 1.23 (initially released on Jun 22, 2022)
+  On Dec 18, 2024 drop support for NumPy 1.24 (initially released on Dec 18, 2022)
+  On Apr 04, 2025 drop support for Python 3.10 (initially released on Oct 04, 2021)
+  On Apr 24, 2026 drop support for Python 3.11 (initially released on Oct 24, 2022)
+
+.. _support_for_other_dependencies:
+
+Support for Other Dependencies
+------------------------------
+
+ASDF also depends on several other Python packages. We currently do not have a
+formal policy for how long we intend to support these dependencies. However, we
+will try to support as many versions of these dependencies as possible.
+
+In general, we will pin each of these dependencies from below with the oldest
+version that we guarantee will work with ASDF. We will also try to test against
+the latest version of each of these dependencies and release bugfixes to supported
+versions of ASDF on an as-needed basis. We will try our best to announce when we
+need to bump the support of these dependencies, and will always record doing so
+(and why) in the changelog.
+
+If you find any issues with ASDF dependencies which affect a currently-supported
+version of ASDF, please open an issue in the ASDF repository.

docs/index.rst

@@ -83,6 +83,7 @@ Resources
 
   asdf/contributing
   asdf/CODE_OF_CONDUCT.md
+  asdf/release_and_support
   asdf/changes
   asdf/citation