[Responder] David Singer
- HTML and other core specifications of the Web platform are processed in an unversioned way in practice. Having an in-band version indicator is misleading to authors, who expect it to have a material effect, and creates a great deal of misunderstanding. - It may be tempting for some implementors to use a standard version indicator as an implementation version indicator. For reasons well-explained by Adam Barth, David Baron and others, this would have an anti-competitive effect on the browser market; content would end up locked in to specific bug profiles. - The proposal not only allows versioning in the doctype but also allows creation of ad-hoc custom doctypes. Profiling the language this way is likely to lead to interoperability problems. - If versioning is to be supported, versioning the doctype is inferior to versioning via an attribute; other specs use an attribute, XML documents generally would not use a doctype, and the doctype is not viable for compound documents such as Atom that embeds XHTML. - The change proposal argues that versioning in the doctype may be useful for controlled environments, but on the other hand argues that versioning must be ignored by implementations. If it has an effect, it creates an interoperability problem; if it has no effect, then it is unclear how it helps controlled environments.