I believe the spec language is unclear here.

It says:

               The 'implicit' alignment of complex elements and groups is the alignment of its child with the greatest alignment.

This could be worded more clearly:

              The 'implicit' alignment of complex elements is the alignment of their model group. The 'implicit' alignment of a model group is the alignment of its child with the greatest alignment. 

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Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com