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- From: Richard Knapp <email@example.com>
- To: "firstname.lastname@example.org" <email@example.com>
- Date: Sat, 10 Mar 2001 09:29:34 -0500 (EST)
Since it isn't quite dead yet (just mortally wouned), I have a question DTD Elements.
Note: Beginner's question is being posed. Please excuse any cases of gross lack of knowledge.
We are working on DTD with the following requirement:
- Base element consists of Child elements First, Second, Third, and Fourth.
- First must appear under Base.
- Second, Third, and Fourth may appear zero or one time.
- Order is not important for elements Second, Third, and Fourth.
The original statement in my DTD was
<!ELEMENT Base (First, Second?, Third?, Fourth?)>
Which imposes an order constraint on the elements. It was suggested that
<!ELEMENT Base (First (Second|Third|Fourth)?)>
was more correct. However, this appears it will allow only Second, Third, _or_ Fourth element, not all three. Is
<!ELEMENT Base (First (Second|Third|Fourth)*)>
seems to allow enough elements (zero or one of each) but also allows more than one.
Is there a good way to address this situation or is this a limit of DTDs? Do Schemas handle this any better?
Again, thank you for you patience.
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