It is not clear why this rule is needed. Surely once a Choice element has been matched there should be no need to read subsequent Choice or Fallback elements at all, but if this sentence is retained then they have to be read to check their attribute values, adding unnecessary processing to the consumer.
Revise the text to address this comment ‘
9.2.1 [28-30]
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Proposed Disposition of DIS 29500 Comment GB-0614 (Modified: 2008-01-02) Agreed; we believe this is confusing and have added the following informative note to Part 5, ยง9.2.1, page 20, line 30, to explain the reasoning: In processing an AlternateContent element, the attributes of every child Choice or Fallback element shall be processed and checked for conformance to this specification, regardless of whether the Choice or Fallback element precedes or follows the selected alternative in markup order. [Note: Checking the conformance of attributes of all Choice and Fallback elements, including those that follow the selected alternative, ensures that conformance violations detected by older markup consumers will also be detected by newer markup consumers that understand additional newer namespaces. end note]
