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I agree that mappings among models are useful.
But I wish to note that the farther one gets away from the hardware the
less robust, slower and harder to optimize the resulting system becomes.
Specifically, if the application design for a terabyte system works out to
be a mapping between an rdbms and an XML tool like TeraText, and then a
separate, different mapping between the XML tool set back to a rdbms, then
my point is that the resulting system will have more failure points, be
harder to tune, and generally less robust than a "native" system.
Mappings, if you ask me, are bridges... like bridges they are an
infrastructure that is high maintenance and which require above normal
attention to support, and are subject to replacement periodically at high
So, it seems to me that just because it can be mapped does not by any means
carry the argument that it should be mapped, or justify the move away from
a dbms into XML.
At 01:13 PM 8/25/2003 -0400, Jonathan Robie wrote:
>At 12:20 PM 8/25/2003, firstname.lastname@example.org wrote:
>>What I mean by that is that XML directly and without interpretation or
>>external normalization has not been show AFAIK to support RM by any proof
>>Of course XML can be normalized into RM. But that does not mean that RM
>>can be normalized into XML, as some have said to my face, and with whom I
>I'm not sure what you are saying. Clearly, any relational database can be
>modeled as XML - for instance, you can use the mappings defined by the
>SQL/XML portion of SQL 2003. When this data is modeled as XML, it is
>represented in the XML model, not in the relational model. Relational data
>can be mapped into XML or viewed as XML, and there are various ways of
>mapping XML into relational data, but each model is its own universe, with
>its own logic.
>>Ergo the discussion.
>>Reconciliation? You mean so that RM is the same as a Tree Model, and
>>vice versa? I suppose a translation or interpretive method can be done,
>>but that does not make RM native to the Tree Model, or vice versa.
>Of course not. Every model is a universe unto itself. Computer Science
>allows more than one model. Mappings among models are useful.
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