RE: [xml-dev] A standard approach to glueing together reusableXML fragments in prose?

["Dare Obasanjo" <dareo@microsoft.com>]

I don't buy your argument. The main point of the relational model is relationships [and tuples]. Although hierarchy is one way to model relationships in XML it isn't the only way. XML 1.0 gives us ID and IDREF. W3C XML Schema gives us xs:key, xs:keyref and xs:unique. 
 
I'd suggest looking at the System.Data.DataSet class in the .NET Framework and seeing how it maps XML structures to relational data to gain an alternate perspective 
 
1.) http://msdn.microsoft.com/library/en-us/cpguide/html/cpconinferringdatasetrelationalstructurefromxml.asp 
 
2.) http://msdn.microsoft.com/library/en-us/cpguide/html/_generating_dataset_relational_structure_from_xsd.asp
 
(1) shows how one could map XML structures to relational tables without schema information while the (2) shows how one could approach this using data from a W3C XML Schema. 

________________________________

From: Rick Marshall [mailto:rjm@zenucom.com]
Sent: Wed 8/20/2003 7:46 AM
To: Chiusano Joseph
Cc: xml-dev@lists.xml.org
Subject: Re: [xml-dev] A standard approach to glueing together reusableXML fragments in prose?



<oxymoron>relationally structured data</oxymoron>

of course you can represent records, but as soon as you make a tree out
of them they're not relational in a database sense

eg

<customer>
        <name>COMPANY X</name>
        <town>SOMEWHERE</town>
        <order>
                <part>ABC123</part>
                <quantity>2</quantity>
        </order>
        <order>
                <part>ABC234</part>
                <quantity>4</quantity>
        </order>
</customer>

just isn't going to be a relational form as there's no way to determine
a priori what the normalised records are. there's clearly 2 tables, and
you know that "customer" has attributes name and town, and "order" has
attributes part and quantity, but it also needs either name or town to
complete the relation and it's not obvious which. either or both?

so without some semantics you can't represent relational tables with the
natural tree structure of xml.

on the other hand

<customer>
        <name>COMPANY X</name>
        <town>SOMEWHERE</town>
</customer>

<order>
        <name>COMPANY X</name>
        <part>ABC123</part>
        <quantity>2</quantity>
</order>
<order>
        <name>COMPANY X</name>
        <part>ABC234</part>
        <quantity>4</quantity>
</order>

is ok, but then from what i've seen on the list most wouldn't think of
this single depth as the natural thing to do.

my personal preference (and used day to day) is:

<table name="customer">
        <record>
                <attribute name="name">COMPANY X</attribute>
                <attribute name="town">SOMEWHERE</attribute>
        </record>
</table>
<table name="order">
        <record>
                <attribute name="name">COMPANY X</attribute>
                <attribute name="part">ABC123</attribute>
                <attribute name="quantity">2</attribute>
        </record>
        <record>
                <attribute name="name">COMPANY X</attribute>
                <attribute name="part">ABC234</attribute>
                <attribute name="quantity">4</attribute>
        </record>
</table>

and a few minor attribute additions. but again i suspect this is not
what most use, but then i'm happy to proved wrong.

rick

On Wed, 2003-08-20 at 22:52, Chiusano Joseph wrote:
> <Quote>
> Unless someone can show me how XML or an XML only tool set such as
> TeraText supports and fulfills RM,
> </Quote>
>
> Are you asserting that one cannot represent relationally structured data
> using XML? If so, can you please elaborate?
>
> Kind Regards,
> Joe Chiusano
> Booz | Allen | Hamilton



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