Re: [xml-dev] Caught napping!

[John Cowan <jcowan@reutershealth.com>]

W. E. Perry wrote:

 > The example I use to illustrate the consequence of this premise is
 > that a natively XML database must be able to commit any well-formed
 > XML instance--and commit it as an instance of the document type
 > described by its root element. It must then be prepared to commit
 > *as a further instance of the same document type* any other
 > well-formed XML document which exhibits the same root element [...].

Why privilege the root element type?  Why not require XML databases
to categorize documents based on the presence of U+2022 in the
value of an attribute named "schritschifchisted" in an element
whose grandparent is "yolki-palki"?

 > This means that only the process can reliably
 > determine whether at the level of its content, not of its
 > structure, a particular XML document can be manipulated by the
 > resources of that process so as to result in the instantiation of
 > the specific data which that process requires.

We've been around this before, but I'll take another swing.
A receiving process that expects to make semantic sense of
documents (as opposed to just blind reformatting or such)
must have knowledge derived from outside itself, or it
cannot interpret the elements and attributes and
character data.

If you don't know any English, it's no use my writing
to you in English, no matter how carefully I explain
myself; and you can't learn English except from people
who already know it.  Complete node autonomy is as
useless as completely private languages.

 >  it may need to selected for processing based on a process' very
 > different understanding of the nature of that content.

Granted.  Where does this understanding come from?

 > In my experience, what this native XML database engine has to do is
 > discover, and then manipulate, the intersection of the properties
 > of data or content in an original instance with the properties of
 > that data which are of use to a particular process.

But if the receiver's understanding of its input is ineffable,
it cannot usefully communicate to the database engine what it
might want.

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