[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XML Schemas: Best Practices
That's a good point ! I guess with allowing any kind of openness and/or extensibility in a conent model, there's a danger of 'losing control' of the original type definition. Would there be any way, if necessary, of limiting the number of times a particular type can be extended ? Hope I'm not heading us off topic here :-) Regards Caroline Jeff Rafter wrote: > > No, using <restriction> does not allow me to put a Reviewer element at > > the top of Book's content model. > > Oof... must have been late-- I don't know what I was thinking. You are > absolutely correct. > > > I don't know what you mean by "multiple layers of inheritance". Could > > you expand upon this please? Thanks! /Roger > > What I meant was certain types may be extended multiple times by different > people. I think the example of BookType is a good one > > <complexType name="BookType"> > <sequence> > <element name="Title" type="string"/> > <element name="Author" type="string"/> > <element name="Date" type="year"/> > <element name="ISBN" type="string"/> > <element name="Publisher" type="string"/> > </sequence> > </complexType> > <complexType name="NonfictionBookType"> > <complexContent> > <extension base="c:BookType"> > <sequence> > <element name="Reference" type="boolean"/> > </sequence> > </extension> > </complexContent> > </complexType> > <complexType name="EncyclopediaBookType"> > <complexContent> > <extension base="c:NonfictionBookType"> > <sequence> > <element name="Volume" type="string"/> > </sequence> > </extension> > </complexContent> > </complexType> > > and so on... "multiple layers of inheritence" is probably bad use of the > terms, but in the above we can see that EncyclopediaBookType extends > NonfictionBookType extends BookType. It seems that if we are planning for > extension we often need to consider that those extensions will be extended, > will be extended... > > Thanks, > Jeff Rafter
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