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The ability to say that an element or group is delimited, but that it is delimited by the boundary of finding the initiator of the next element or group would simplify the description of many formats.
Another formulation would be to specify that an element/group is delimited, but that the terminating markup is not consumed, and hence, must be consumed by whatever comes next in the model.
Character Class Entities
We badly need an entity that means 'any whitespace that is not a line ending'. This avoids the specification of separators like:
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