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What you call the "include" style of design, more commonly called
"modularized", is commonly used both with DTDs and XSDs in
environments with multiple related models.
Here, on XML-DEV, you are likely to hear that DTDs are un-cool and
everyone one should be using XSD or RELAX NG. I suggest that instead
of caving in to this pressure you look at what you want to model,
what sorts of constraints on document content you want to express,
and select your modeling language(s) based on those requirements. In
all cases you can, and based on you note, probably should, modularize
For an example of a set of DTDs that has been modularized for just
that reason take a look at the DTDs at: http://dtd.nlm.nih.gov/ and
the description on that page of the Suite of Modules.
(OH - the file name doesn't matter; you can call the modules .mod, or
.ent, or .dtd, or whatever you like. In DTDs they use DTD syntax, in
XSDs they use XSD markup, etc. There is no ".mod" format, at least
not as an XML modeling format.)
>Hopefully this is an easy question to answer.
>I'm building an article/publication based website and was planning
>on storing most of the content for the site in XML (for
>manageability, automation and sharing purposes). I'm currently
>designing the layout for the XML files and I want to create a DTD
>(or XSD) to describe the various types of XML files we will be using
>throughout the site. In doing this I've begun to realize that
>several elements are actually being reused across various XML
>documents. My question is this:
>Is there a way to include elements in a DTD (or XSD) that are
>defined in another file? It appears as if the w3 is doing this with
>XHTML using "mod" files, but I'm unfamiliar with the format, and
>(unfortunately) not an XML expert. Is it possible to define single
>or related elements in their own files and then include them as
>needed in various DTDs through some sort of "include statement"?
>Does XML Schema support this as well? Are their any problems with
>laying out my DTDs (or XSDs) in this "include" style of design?
B. Tommie Usdin mailto:firstname.lastname@example.org
Mulberry Technologies, Inc. http://www.mulberrytech.com
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