[mgabka]

The existing support levels did not fully reflect their intended purpose. In practice, once an ACLE feature reached Beta and was implemented in a compiler, introducing backward-incompatible changes was already highly undesirable.

ACLE changes are generally introduced in an additive manner to preserve compatibility with existing code.

To better reflect this approach, replace the three existing support levels with two specification maturity levels: Alpha and Complete.

As for any pull request, please make sure to go through the below
checklist.

Checklist: (mark with X those which apply)

• If an issue reporting the bug exists, I have mentioned it in the
  PR (do not bother creating the issue if all you want to do is
  fixing the bug yourself).
• I have added/updated the SPDX-FileCopyrightText lines on top
  of any file I have edited. Format is SPDX-FileCopyrightText: Copyright {year} {entity or name} <{contact informations}>
  (Please update existing copyright lines if applicable. You can
  specify year ranges with hyphen , as in 2017-2019, and use
  commas to separate gaps, as in 2018-2020, 2022).
• I have updated the Copyright section of the sources of the
  specification I have edited (this will show up in the text
  rendered in the PDF and other output format supported). The
  format is the same described in the previous item.
• I have run the CI scripts (if applicable, as they might be
  tricky to set up on non-*nix machines). The sequence can be
  found in the contribution
  guidelines. Don't
  worry if you cannot run these scripts on your machine, your
  patch will be automatically checked in the Actions of the pull
  request.
• [ X] I have added an item that describes the changes I have
  introduced in this PR in section Changelog for year 20xx (this year)
  of section Preface/About this document.
  Create Changelog for year 20xx if it does not exist. Notice that
  changes that are not modifying the content and rendering of the
  specifications (both HTML and PDF) do not need to be listed.
• When modifying content and/or its rendering, I have checked the
  correctness of the result in the PDF output (please refer to the
  instructions on how to build the PDFs
  locally).
• Please DO NOT add my GitHub profile to the list of contributors
  in the README page of the project.

[mgabka]

The CI is most likely failing due the fact that there are some features currently at the beta support level. They would most likely need to be removed from beta, but I would do it as a separate PR and rebase this one, if the new proposed maturity levels are looking fine to reviewers.

[paulwalker-arm]

You've only changed one of many instances?

I'm not sure it's worth changing but if you really want to then I think This feature's maturity level is [***Alpha***]. reads better. I'd also remove the "and might change....." part because that should be clear when reading what a maturity level of Alpha means.

[paulwalker-arm]

Perhaps worth mentioning the feature can be removed?

[paulwalker-arm]

Not sure we should describe how we get to the complete stage. Perhaps just say what it means, specifically that any changes will be backward compatible.

Is it worth adding advice to the "Maturity levels" chapter for what a user of a feature at Alpha maturity level can do to signal their desire to use it in production code? Perhaps raise a GitHub issue?

[paulwalker-arm]

Suggested change

	The following maturity levels are used by the ACLE specifications:
	All features have one of the following maturity levels. When no maturity level is specified, the feature is considered complete.

Keeps the relevant clauses together.