[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XML Schemas: Best Practices - Chameleon design
Yes it *would* be a good thing if it worked. But as long as we have an <include> rather than an <import> we run the risk of getting too much rubbish that we don't want. I certainly expect my re-usable (chameleon) schemas to grow as we develop our schema set over the next five years. Since we anticipate growth rather than change in the chameleon schemas, I want this to be safe for all existing schemas that are using the definitions in the chameleon schema. But it isn't! Name collisions could suddenly appear in "stable" schemas as the chameleon schema grows. So now we need much tighter (and possibly impossible to manage) version control. Using proxy schemas doesn't help me as I want the names to be in the "target" namespace. Now I will disagree with Roger. He says that "As we saw above, the Chameleon Namespace design approach has restrictions on how the no-namespace components must be designed for them to be usable by other schemas. Namely, they must not reference one another. The components must be decoupled (which is a desirable trait)." I disagree that this is a desirable trait. I want several complex data types to use a common simple type that I have defined. "ZipCode" might be an example. Doing this seems to me to be a desirable trait, but I can't with a nonamespace schema. So with a large schema base, I am stuck. I am not sure whether there are things we can do with elementFormDefault="unqualified" that would help here. I would sure like help to examine it. Does Henry T have a view? I think we are working here in possibly the most important aspect of schema design at the moment since bottoming out schema re-use is vital to any migration towards a semantic web. Great stuff Roger and the rest of you! Meanwhile, did my last message make the list? I realise Roger got it, but I got a bounce from the mail server "550 <xml-dev@l...>... Host unknown Name server: smtp.elistx.com.: host not found)". Paul Spencer Author: XML Design and Implementation (Wrox Press) Co-author: Beginning XML (Wrox Press) Boynings Consulting - Delivering XML to industry and government http://www.boynings.co.uk/ -----Original Message----- From: Thomas B. Passin [mailto:tpassin@h...] Sent: 07 November 2000 14:04 To: Roger L. Costello; xml-dev@l... Subject: Re: XML Schemas: Best Practices - Chameleon design Schema omponents, when included into a schema, take on the parent schema's target namespace, if they are not already in it or don't have one of their own. This suddenly reminded me of the new import syntax in Python (I don't know how many other languages already have it too): import spam as eggs This lets you have your cake and eat it too - your components can be referred to by any namespace you want. Seems to me that this is very close to what Cameleon provides. This sounds like a GOOD THING to me. Cheers, Tom Passin
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