xml-dev - DTD design

[heiko.grussbach@crpht.lu]

Hi,

I have the following problem, I want to define an element E that may
contain elements A,B,C. Order should be insignificant and A,B and C are all
optional. Furthermore, A,B and C may each be replaced by X.
The first example was simply like this:

<!ELEMENT E (
     ( A?, B? ) |
     ( B?, A? ) |
     ( A?, X? ) |
     ( B?, X? ) |
     ( X?, A? ) |
     ( X?, B? ) |
     ( X?, X? )
) >

My XML-editor (XMetal 1.2) reports an ambigous content model error. After carefully studying the appendix of the XML rec, and with some help
by the support of XMetaL , I came up with the following:

<!ELEMENT E (
     EMPTY |
     (A,(B|X)?) |
     (B,(A|X)?) |
     (X,(A|B|X)?)
)>

Is this the best solution?, What if there are more childs, like A,B,C,D etc. Wouldn't the DTD just explode?

Regards

Heiko Grussbach


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