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Subject: Lists of simple datatypes
At the moment, TREX does not allow things like: <zeroOrMore> <data type="xsd:integer"/> </zeroOrMore> There is a fairly obvious semantic that could be given to this: it would match a list of zero of more integers separated by whitespace. This is the same semantic as "list" in W3C Schemas. I believe the XML Query Algebra takes this approach: it uses the normal sequencing operators to model XML Schema list simple types. It is not entirely trivial to make this work, both from the point of view of the formal specification and from the point of view of the implementation. There would definitely be a complexity cost in making this work. One benefit of this might be to allow us to have a simpler interface to the datatyping vocabulary. XML Schemas offers 3 ways of deriving new simple types: union, list, restriction. TREX can already handle union (it's the same as choice). If we can also handle list, that leaves only restriction. If we only have to support restriction, we could appeal to an external datatype language purely for facets, rather than for ways of deriving datatypes. For example, we might do: <data type="xsd:integer"> <xsd:minInclusive trex:role="facet" value="10"/> </data> instead of <data type="xsd:integer"> <xsd:simpleType trex:role="datatype"> <xsd:restriction base="xsd:integer"> <xsd:minInclusive value="10"/> </xsd:restriction> <xsd:simpleType> </data> Better yet if we could find a way to make: <data type="xsd:integer" xsd:minInclusive="10"/> work. I think this would be significantly easier to learn and use than the current syntax. Is this an avenue of development worth pursuing? James
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