4.1.1 requires that Web content to be parsed unambiguously. Does this require the formal specifications be open, so that new user agents can parse the content? For example, suppose the baseline specifies just one Web browser, that implements rules for applying defaults to resolve any potential ambiguities in HTML that might be interpreted differently if another browser were used; is the HTML parsable unambiguously within the scope of the baseline? As another example, suppose a Web uses a proprietary data format that only a single plug-in can render; does it matter if it's parsable unambiguously if there is only one renderer?
Insert the phrase ", using publicly available specifications", to read "Web units or authored components can be parsed unambiguously, using publicly available specifications, and the relationships in the resulting data structure are also unambiguous.
To make this requirement easier to understand, we have reworded SC 4.1.1 to clarify that it must be possible to parse content without the need for user agent repair. The revised SC reads as follows:
4.1.1 Content implemented using markup languages has elements with complete start and end tags, except as allowed by their specifications, and are nested according to their specifications. (Level A)
Note: Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute value quote are not complete.