You got this one exactly right. Not only is the "extensibility" issue poorly defined, but it runs contrary to the conclusion of the article! (that multiple languages and syntaxes can be represented in a single, semantically monolithic, language-neutral XML format [which is a dubious claim]).
It seems like 'extensibility' is really little more than a marketing 'gimmick' word anyway, since "code comments" are a feature of nearly every language, and really the only way to introduce things that the original language designers *never imagined to begin with* (which is how I would define true 'extensibility').
The problem is all those different languages are out there for a reason. If it were trivial to port Perl into Java (and vice versa) it would be done already.
XML has nothing to do with it. In fact, XML would make it even *more* difficult because you would have to escape all the funky character sequences that cause XML to choke! How would you (for example) store XML code that outputs XML? You have to introduce a bunch of escape sequences.. but what if you want to represent code that outputs escape sequences? You need a way to escape the escapes... This would be a nightmare to develop and it would be unreadable (thus ruining the 'extensibility' you supposedly get from XML in the first place)
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You got this one exactly right. Not only is the "extensibility" issue poorly defined, but it runs contrary to the conclusion of the article! (that multiple languages and syntaxes can be represented in a single, semantically monolithic, language-neutral XML format [which is a dubious claim]). It seems like 'extensibility' is really little more than a marketing 'gimmick' word anyway, since "code comments" are a feature of nearly every language, and really the only way to introduce things that the original language designers *never imagined to begin with* (which is how I would define true 'extensibility').
The problem is all those different languages are out there for a reason. If it were trivial to port Perl into Java (and vice versa) it would be done already. XML has nothing to do with it. In fact, XML would make it even *more* difficult because you would have to escape all the funky character sequences that cause XML to choke! How would you (for example) store XML code that outputs XML? You have to introduce a bunch of escape sequences .. but what if you want to represent code that outputs escape sequences? You need a way to escape the escapes ... This would be a nightmare to develop and it would be unreadable (thus ruining the 'extensibility' you supposedly get from XML in the first place)