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Use substitutionGroups to make the syntax easier to work with both with respect to selectors, by eliminating need for xsi:type, nd for humans. There are three places in the existing schema where this might apply: (1) For expressions, to eliminate the need for xsi:type This is largely a matter of turning named complex types into elements. See xqx.newschema1.xsd and xq.ex1.xml (2) For steps in path expressions. This amounts to converting the simple type enumeration into a collection of elements. See xqx.newschema2.xsd and xq.ex2.xml (3) For operators. This involves converting some types to elements and various enumerations to elements. Since some of the operator names are non valid as element names, names need to be created for these cases. See xqx.newschema3.xsd and xq.ex3.xml (1) and (2) aren't necessary to get rid of xsi:type, but they do provide for a more direct syntax. One could go even further on (c) and put the operators into the "op:" namespace:, which might assist in automatic mapping from XQuery grammar. See schemas and examples at http://lists.w3.org/Archives/Member/w3c-archive/ 2005May/0068.html
(On behalf of Schema WG)
The Query WG has considered your comment and agrees with it. A new XQueryX schema has been developed that uses substitution groups in preference to the previous hierarchial approach. When a new edition of the XQueryX spec is published, we hope that you will review it and, if, you find the changes satisfactory, mark this comment as CLOSED. We appreciate your feedback on the XML Query specifications. Please let us know if this response is satisfactory. If not, please respond to this message, explaining your concerns. Jim Melton On behalf of the XML Query Working Group
The Schema WG is satisfied with this resolution.