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   Re: [xml-dev] Adam Bosworth Article - what does "directaccess" mean?

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Here's a Water program that creates a class, defines a method,
creates an instance, and call a method on the instance.

<defclass company stock_symbol price revenue expenses>
 <defmethod PE_ratio>
   .price.<divide .revenue.<minus .expenses/> />



----- Original Message -----
From: "Jonathan Robie" <jonathan.robie@datadirect-technologies.com>
To: "W. E. Perry" <wperry@fiduciary.com>; "XML DEV"
Sent: Friday, January 17, 2003 4:02 PM
Subject: Re: [xml-dev] Adam Bosworth Article - what does
"directaccess" m ean?

> At 11:15 AM 1/16/2003 -0500, W. E. Perry wrote:
> >Jonathan Robie wrote:
> >
> > > In XQuery, you can remain loosely coupled while improving the
> > > ratio of your code. The following computes the PE Ratio for IBM:
> > >
> > >     let $stock := document("stocks.xml")/stock[@id="IBM"]
> > >     return $stock/price / ($stock/revenues - $stock/expenses)
> > >
> > > I do think this is more elegant than the equivalent SAX or DOM.
It is no
> > > more tightly coupled.
> >
> >Oh yes it is. This code presupposes  1) a document of a given name;
> I was trying to write something equivalent to Adam's DOM sample,
which does
> specify the name. However, I agree that there can be real advantages
> accessing this through input() so that any document can be accessed
in this
> manner:
> let $stock := input()/stock[@id="IBM"]
> return $stock/price / ($stock/revenues - $stock/expenses)
> >2) a specifically-labelled ("IBM") ID on an element in that
document; 3)
> >specifically-labelled 'price' and 'revenue' information items which
are 4)
> >specifically presupposed to be part of that document (as opposed to
> >separately computable or capable of being looked up in some place
of greater
> >local interest, such as the last trade in a particular market)
> Walter, either the DOM program or the XQuery program can look up the
> before using them, and that does provide more flexibility, but
again, I was
> trying to compare apples to apples, and the DOM fragments that Adam
> do not do this.
> >and 5) [most crucial of all unexamined assumptions here]
presupposed to be
> >in a form
> >against which the computation expressed in the code is directly
> >(though, of course as 'real' XML the only form that they would
necessarily be
> >in is Unicode text).
> No, the XQuery I showed you does not make this assumption.
> The data might be in an XML document that can be accessed and parsed
> the document() function, or it might be in a view of some other
> such as a relational database.
> Jonathan
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