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   Re: [xml-dev] XML-enabled databases, XQuery APIs

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We're talking apples and oranges here.

What you're talking about is a generic set of relational tables like 
Elements, Attributes, Text, Comments, and ProcessingInstructions. This 
is generally considered to be a native XML database implemented on top 
of a relational database. In fact, this is roughly how SQL Server 
implements their XML data type.

What I'm talking about is a set of tables designed to store documents 
corresponding to a particular XML schema. For example, mapping a sales 
order document to the Sales, Items, Customers, and Parts tables. While 
such tables can, in theory, store things like sibling order, comments, 
and processing instructions, in practice they almost never do. This is 
generally known as "shredding".

One significant difference between the two is that the first in some way 
looks like an XML document while the second is indistinguishable from 
other relational data.

-- Ron

Peter Hunsberger wrote:
> On 4/15/05, Ronald Bourret <rpbourret@rpbourret.com> wrote:
>>However, shredding shouldn't be viewed as a substitute for native XML
>>data storage as it doesn't preserve sibling order, comments, processing
>>instructions, etc. and usually doesn't support mixed content. It also
>>requires design-time mapping of the XML schema to the relational schema
>>-- something that won't work with schemaless documents. So it shouldn't
>>be viewed as a substitute for native XML storage but as a complementary
> I think you're over generalizing more than a bit. Over the years I've
> done a couple shredding implementations.  In particular, I've
> previously built a generalized approach on top of SQL server that
> supported mixed content, sibling order and did not require a schema. 
> Adding comments and PI's to that would have been pretty much trivial. 
> There's nothing magic here; generalized hierarchical to relational
> mapping algorithms have been around for a long time...


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