ISO/TC 211 Geographic Information/Geomatics  has published the standard ISO 19139 Geographic information -- Metadata -- XML schema implementation  which informatively references the XML schema  which in turn calls an OGC schema  for the W3C xlink 1999 namespace  because there was no XML schema published for the 1999 version of xlink.
I’ve not checked the differences between the two schemata which refer to the same namespace, but, you may wish to liaise with OGC or ISO to update this link in step with your developments in order to improve adoption of your new work. If not you may find that any incompatibilities between the informative OGC schema and your informative schema may cause delays to the adoption of your schema.
You will note that this does have attribute groups defined (as well as
model groups and complex types), but does not use the same names that
the opengis schema uses.
Henry S. Thompson, School of Informatics, University of Edinburgh
Half-time member of W3C Team
10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 651-1426, e-mail: [hidden email] URL: http://www.ltg.ed.ac.uk/~ht/ [mail really from me _always_ has this .sig -- mail without it is forged spam]
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