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Ronald Bourret wrote: > Elliotte Rusty Harold wrote: > > > I'm beginning to notice this as one of the fundamental confusions. > > There is no problem here. Each namespace has (or may have) its own > > RDDL document. A RDDL document describes a *namespace*. A RDDL > > document does not describe a *document*. There is not, nor was there > > ever intended to be, one canonical RDDL document for any given > > document. > > While I agree that this is what RDDL is designed to solve, I think that > what Nicolas is asking for -- a document describing a given doctype -- > is much more useful. Let me propose this: A document type can be defined by a schema (a literal example is a DTD) and consists of the set of all documents which are valid with respect to the schema. Note that validity with respect to the schema is a property defined by the individual schema definition language. A document is a member of the 'document type set' if it is valid with respect to the defining schema. A document may be valid with respect to an infinite number of schemas, hence may have an infinite number of types. This all is outlined in http://www.openhealth.org/RDDL/SchemaAlgebra in particular [7] typeOf(x,c) := x in Instances(c) where "x" is a document and Instances(c) is defined by: [2] Instances(A) := for all a such that valid(a,A) implies a in Instances(A) and where valid(a,A) means that "a" is valid with respect to the schema A. > > RDDL is like handing the end user of a TV set a bunch of different > manuals describing switches, CRTs, integrated circuits, and electric > cords. While a user can figure out how to turn on the TV set and adjust > the volume from these manuals, it is unlikely they will do so. > > In documentation terms, RDDL is a reference manual and only low-level > people (e.g. TV repairmen) want reference manuals. Everybody else wants > a user's guide. > Although this is outside the scope of the current RDDL specification, you make a persuasive argument that the functionality is desirable, and I do believe RDDL can assist with an acceptable solution. The 'problem' is that a given document does not define a single document type, nor does a namespace define a document type, so that a mechanism is required to indicate which 'type set' a document is intended to belong to. e.g. <!DOCTYPE or xsi:schemaLocation="..." How might RDDL help? Perhaps we could define a _purpose_ to indicate document type: http://www.rddl.org/purposes#document-type and then the _set_ of all document types an instance is intended to belong to would be referenced by the set of all rddl:resources that have this purpose, but whose nature indicates the particular schema definition language used to define the type. We still need a means to connect the instance to the document type set definition. It would be really nice to use the <!DOCTYPE declaration for this, but this has already been hardwired to DTDs... and so the Public Identifier cannot be connected to a RDDL document by this mechanism. Perhaps an attribute: <root rddl:doctype="....a RDDL directory of 'document types' ..."> Jonathan
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