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Re: "Query by example" (was Re: misprocessing namesp

• To: elenz@x..., gtn@r..., xml-dev@l...
• Subject: Re: "Query by example" (was Re: misprocessing namespaces)
• From: "Wayne Steele" <xmlmaster@h...>
• Date: Thu, 31 Jan 2002 13:21:14 -0800
• Bcc:

XML-QL[1] also has a nice "QBE" type syntax, but in a non-XML language:

WHERE
<cars>
   <car><MakeModel>Ford</></> element_as $car
</>
IN "someDataSource"
CONSTRUCT $car

As you mentioned, it great for simple things, and can't handle XPaths.

-Wayne Steele

[1] http://www.w3.org/TR/NOTE-xml-ql/


>From: "Evan Lenz" <elenz@x...>
>To: "Gavin Thomas Nicol" <gtn@r...>, "The Deviants" 
><xml-dev@l...>
>Subject:  "Query by example" (was Re:  misprocessing 
>namespaces)
>Date: Thu, 31 Jan 2002 09:12:54 -0800
>
>Gavin Thomas Nicol wrote:
> > The idea was "match by example", where you'd
> > give a sample XML fragment as the pattern to match. It was supposed to
> > be like "query by example"....
>
>The "query by example" approach can only get you so far. For example, this
>XPath expression:
>
>   /Cars/Car[contains(MakeModel,'ford')]
>
>could easily be formed in XML syntax as follows:
>
>   <Cars>
>     <Car>
>       <MakeModel>Ford</MakeModel>
>     </Car>
>   </Cars>
>
>This is reminiscent of Examplotron[1]. The primary difference is that
>Examplotron is "schema by example", where our intent here is "query by
>example".
>
>The difficulty of this approach arises when you try to accommodate the 
>XPath
>axes. Soon, the benefits of the XML syntax start to diminish. A different
>approach would have to be taken, such as Wayne Steele's contribution[2] 
>last
>March. That XML tools could then be used on XPath is valuable, but this no
>longer possesses the simplicity and intuitiveness of a "query by example"
>approach.
>
>That said, "query by example" works beautifully for applications that don't
>need as powerful a query language as, say, XQuery. For applications that
>simply require the extraction of XML fragments from large repositories of
>XML documents based on certain search criteria, a simple XML-based "query 
>by
>example" approach is sufficient, with more sophisticated processing (e.g.
>XSLT) commencing outside the database.
>
><proprietaryExample product="XYZFind Server">
>Query for all cars such that 'Color' contains "white", 'MakeModel' contains
>"ford" and 'Price' is less than or equal to "$15,000":
>
>   <xyz:input xmlns:xyz="http://xyzfind.com...">
>     <xyz:query>
>       <Cars xyz:return="no">
>         <Car xyz:return="yes">
>           <MakeModel>ford</MakeModel>
>           <Price><xyz:number le="15000"/></Price>
>           <Color>white</Color>
>         </Car>
>       </Cars>
>     </xyz:query>
>   </xyz:input>
>
></proprietaryExample>
>
>Evan Lenz
>http://www.xyzfind.com
>
>[1] http://examplotron.org/
>[2] http://www.xmlhack.com/read.php?item=1118
>
>
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