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Re: [csswg-drafts] Versioning policy and backwards incompatible changes (#5114)

From: Sam Sneddon via GitHub <sysbot+gh@w3.org>
Date: Tue, 26 May 2020 23:34:19 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-634335136-1590536058-sysbot+gh@w3.org>
> I don't think we will have a normative definition of Level 2 at that point. It'll be obsoleted just as much as CSS 1 is. We're not far from that point already.
…
> We sometimes remove things because we prefer the levels to not contradict each other, just for confusion-avoidance reasons, but there's no sense in which an earlier level is a meaningful artifact which an implementor can decide to support vs a later level. They're just previous versions of the current document, is all.

Yet we [define levels in Snapshot](https://www.w3.org/TR/CSS/#css-levels) as:

> Cascading Style Sheets does not have versions in the traditional sense; instead it has levels. Each level of CSS builds on the previous, refining definitions and adding features. The feature set of each higher level is a superset of any lower level, and the behavior allowed for a given feature in a higher level is a subset of that allowed in the lower levels. A user agent conforming to a higher level of CSS is thus also conformant to all lower levels.

To me this strongly implies we view support for each level as meaningful. Likewise, the fact we bother to define what Level 1 constitutes also implies we consider it a meaningful artifact; if it's in fact just a previous version of the document then surely there's no point in defining what Level 1 is?

> CSS2 had a lot of stuff declared undefined near the end of its process, not because of backwards-incompatible changes in the level 3 module, but because the behavior wasn't yet consistent between browsers and so we couldn't get 2+ passes for tests for any reasonable defined behavior.
>
> Since then, I don't think we've gone back and undefined things because of a change in later versions, have we?

I could swear we had; we've definitely upon occasion discussed making things undefined (which is equivalent to removing them, no?).

As a meta point: that the fairly new editor of CSS2 disagrees with others about what the WG policy is on maintaining older versions of spec text is says something about the WG, and it isn't good. We *really* need to better document (in a discoverable way!) cross-spec policy decisions for things like that.

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Received on Tuesday, 26 May 2020 23:34:22 UTC

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