When alignmentUnits='bits', the rule highlighted below looks rather hard to justify. We should either a) remove the rule entirely and allow any postiive integer > 1 or b) make the rule apply only when alignmentUnits='bytes' I favour a) because it's less work for an implementer. alignment Non-negative integer or 'implicit' A non-negative number that gives the alignment required for the beginning of the item. If alignment is required then the size of the AlignmentFill grammar region will be non-zero if the item must be aligned to a boundary. ‘implicit' specifies that the natural alignment for the representation type is used. See the table of implicit alignments Table 11 Implicit Alignment in bits If alignment is 'implicit' then alignmentUnits is ignored. Values are usually 1, 2, 4, 8, 16 to match memory word alignment boundaries, 4096 to match page alignment boundaries. However, any non-negative integer power of 2 is allowed. Annotation: dfdl:element, dfdl:simpleType, dfdl:sequence, dfdl:choice, dfdl:group alignmentUnits Enum Valid values are ‘bits’ or ‘bytes’ Scales the alignment so alignment can be specified in either units of bits or units of bytes. Annotation: dfdl:element, dfdl:simpleType, dfdl:sequence, dfdl:choice, dfdl:group regards, Tim Kimber, Common Transformation Team, Hursley, UK Internet: kimbert@uk.ibm.com Tel. 01962-816742 Internal tel. 246742 Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU