xml-dev - Layers, again (was Re: fixing (just) namespaces and validation)

[David Megginson <david@megginson.com>]

David Carlisle writes:

 > Yes, agreed, it wasn't really a criticism. The fact remains that at
 > the current time the `problem' is that there is no standard way of
 > getting from one layer to the other.

Sure there is -- at least, the Namespaces REC defines pretty clearly
what Namespace declarations and prefixes do.

 > That is, if I have a namespace aware application that really
 > doesn't mind what prefix is used in a document instance, there is
 > no convenient standard way of supplying a DTD against which a set
 > of documents to be used with that application may be validated.

But that's not a problem of getting from one layer to another; it's
simply a problem of applying an operation to a layer.  Here's one
layered view:


Layer 1: octets
Validate with: (custom code)

Layer 2: Unicode characters
Validate with: (regular expression)

Layer 3: XML
Validate with: DTD

Layer 4: Namespaces
Validate with: (XML Schemas, eventually)

Layer 5: RDF
Validate with: RDF schema

Layer 6: Application
Validate with: (local business rules)


Here's another layered view:


Layer 1: octets
Validate with: (custom code)

Layer 2: Unicode characters
Validate with: (regular expression)

Layer 3: XML
Validate with: DTD

Layer 4: Namespaces
Validate with: (XML Schemas, eventually)

Layer 5: XHTML
Validate with: (built-in XHTML processing rules)

Layer 6: Application
Validate with: (local business rules)


My applications have no problem at all getting from layer 3 to layer 4
in either example, because the path is fairly well defined; it just
happens that there is also a convenient schema formats for applying
structural validation or guided authoring to layer 3, but that's a
separate operation applied to the layer, not part of the layer
itself.  Many layers do not have a standard validation technique yet.


All the best,


David

-- 
David Megginson                 david@megginson.com
           http://www.megginson.com/

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