Dear Scott,

This is an interesting point.

I understand that the 3-level of abstractions for modeling data, Conceptual,
Logical, and Physical are difference as follow:
Conceptual: the model at this level is platform-independent and also could
be logically modeled using any modeling technique, ERD, OO model, or XML
Schema.
Logical: is also platform-independent but it is based on specific modeling
technique.
Physical: is platform dependent.

These three concepts have been addressed very well in the area of DB data
modeling. You will find the ER modeling tools, such as power designer,
supporting the three levels, but the the context of RDB.

However, in the area of XML, I did not come across any paper regarding that.

I agree with you that "I would say that an XML schema would correspond to
the logical data model"

Because, XML schema is based on a specific model and at the same time is
platform-independent.

from my point of view, the implementation of the XML Schema  is a physical
model that is platform dependent.

I do believe that as the ER modeling tools, supported the three levels of
abstractions,  an XML Schema modeling tool could support these three level.


Best Regards,
Essam Mansour

On Jan 29, 2008 4:20 AM, Tsao, Scott <scott.tsao@b...> wrote:

>  I recently read an article A Few Thoughts on Data Modeling and Kids'
> Soccer - An Interview with William G. Smith<http://www.wilshireconferences.com/interviews/smith.htm>.
> In this article Mr. Smith advocates a 3-schema architecture for data
> modeling, i.e., Conceptual, Logical, and Physical data models.  I
> understand that this architecture has been a popular approach by information
> architects in the late 80's to early 90's, under the banner of Data or
> Information Resource Management (DRM or IRM).
>
> It seems to me that, other than the Conceptual data model, the Logical and
> Physical data models no longer directly apply to the XML approach of data
> modeling (e.g., using the W3C XML Schema).  For example, Mr. Smith talks
> about a 3NF logical data model, which only applies when one is taking a
> strictly 'relational' approach.  So, I was wondering if there is a parallel
> sets of data models in the XML-based data modeling world.
>
> Based on my (limited) understanding of the purpose and techniques
> mentioned in the article, I would say that an XML schema would correspond to
> the logical data model, and an XML binding (to a particular database or
> programming language) would correspond to the physical data model.  In
> addition, transformation or mapping between logical and physical data models
> could be implemented by adopting a standard such as SQL/XML.
>
> Could anyone on this list help me to gain a understanding on this issue?
>
>
> Thanks,
>
> *Scott Tsao*
> Associate Technical Fellow
> The Boeing Company
>