[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Creating a single XML vocabulary that is appropriately cus
> How do you create a single XML vocabulary, and validate that XML > vocabulary, for a community that has sub-groups that have overlapping > but different data needs? With difficulty. I've seen the problem more often in a different guise: how do you design a set of 400 messages for application data interchange that reflect different information about different events affecting the same objects? One approach is to rediscover the concept of subschemas, as used in the Codasyl database model. (In the relational model, these became views, but that's a less useful concept in this context.) You can start with a schema that makes everything mandatory, and construct from it a subschema in which parts are optional and/or prohibited. Or you can start with a schema in which everything is optional, and your subschema can make some parts mandatory. Either way, I think you are using some kind of process that modifies a schema to create a different schema. Plenty of users are doing such things by applying XSLT transformations to XSD documents, but it's not easy. Others are doing it using xs:redefines, which is not much better. Others are simply giving up: I've seen users stuff unwanted data into a message because it's too hard to change the schema to make it optional, and I've seen users relax the schema to make an element optional for everybody even though there are some contexts where it's required. Assertions in XSD 1.1 could be used to make the process much easier. If your schema is permissive (everything optional), you can add assertions to make it more constrained. Michael Kay http://www.saxonica.com/
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