[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Restriction in XML Schema
Jay Zhang <jz@i...> writes: > The definition of restriction in XML Schema reads: > > >A type definition whose declarations or facets are in a > >one-to-one relation with those of another specified type > >definition, with each in turn restricting the possibilities > >of the one it corresponds to, is said to be a restriction. Note this is an introductory summary early in the spec. > Would this definition make syntactic coincidence unduely > significant? > > Let me illustrate with an example: > > Let me define a base type 'fields' as: > > <complexType name='fields'> > <sequence> > <element name='field' maxOccurs='Unbound'/> > </sequence> > </complexType> > > would the following derived type have violated the definition > of restriction? > > <complexType name='myfields'> > <complexContent> > <restriction base='fields'> > <sequence> > <element name='field' tag='15A'/> > <element name='field' tag='20'/ > </sequence> > </restriction> > </<complexContent> > </complexType> Not sure what you mean by "tag='15A'" -- this is not valid XML Schema syntax? Leaving those out, your derivation is OK. > However, if we define base type fields to be an equivalent: > > <complexType name='fields'> > <sequence> > <element name='field' maxOccurs='Unbound'/> > <element name='field' minOccurs='0' maxOccurs='Unbound'/> > </sequence> > </complexType> This type violates the Unique Particle Attribution constraint, and is not necessary for valid restriction, anyway. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2001, part-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@c... URL: http://www.ltg.ed.ac.uk/~ht/
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