Frank Ellermann scripsit: > Right, now I also see it. An enumeration is useful if > it could be mistaken as well-formed "regular" tag. For > a parser it's important to match some "irregular" tags > _before_ it starts to match the "regular" tags. A non-validating parser doesn't have to distinguish between semantically decomposable tags and indecomposable ones with special meanings. All it has to do is have an ABNF that specifies what tags do and don't match, to which it also must add the rule against repeated singletons. For that purpose, only the irregular-syntax tags need to appear in the ABNF; the ones with regular syntax but irregular semantics do not. > From that POV x-anything and i-anything are harmless, i-anything is *not* harmless; it means that i-foobar is well-formed even though it is neither composed of valid subtags nor itself a valid grandfathered tag. i-foobar should be ill-formed. Validating parsers can use a different set of productions if it suits them better, though I don't see why it would: the simplest approach is to check for well-formedness, then check the registry to see if the tag is grandfathered, and if not, decompose them. -- John Cowan http://ccil.org/~cowan cowan at ccil.org Monday we watch-a Firefly's house, but he no come out. He wasn't home. Tuesday we go to the ball game, but he fool us. He no show up. Wednesday he go to the ball game, and we fool him. We no show up. Thursday was a double-header. Nobody show up. Friday it rained all day. There was no ball game, so we stayed home and we listened to it on-a the radio. --Chicolini _______________________________________________ Ltru mailing list Ltru at ietf.org https://www1.ietf.org/mailman/listinfo/ltru
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