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RE: meaning of (salary, bonus)

From: Howard Katz <howardk@fatdog.com>
Date: Tue, 7 Jan 2003 20:37:05 -0800
To: "Mary Fernandez" <mff@research.att.com>
Cc: "Michael Kay" <Michael.Kay@softwareag.com>, <www-ql@w3.org>
Message-ID: <NFBBKEMEJKFJGCPOOKHCAEMICOAA.howardk@fatdog.com>

What happens in the case of a mixed sequence such as

        (salary, 3, bonus)[. > 0 ]

Is the ordering implementation-dependent?

Howard

> -----Original Message-----
> From: www-ql-request@w3.org [mailto:www-ql-request@w3.org]On Behalf Of
> Mary Fernandez
> Sent: Tuesday, January 07, 2003 6:55 PM
> To: Howard Katz
> Cc: Michael Kay; www-ql@w3.org
> Subject: RE: meaning of (salary, bonus)
>
> In the *sequence* expression:
>
>   (salary, bonus)
>
> all salary elements will precede all bonus elements.
>
> In the *path* expression:
>
>   (salary, bonus)[. > 0]
>
> the resulting salary and bonus elements whose content is greater
> than zero will be in document order.  This is because
> path expressions always yield sequences of nodes in document order
> whereas sequence expressions yield sequences of nodes in input order.
>
> On Tue, 2003-01-07 at 13:59, Howard Katz wrote:
> >
> > Thanks Michael and everyone, that's helpful.
> >
> > One additional question. I'm unclear about the concept of
> "document order"
> > and when that applies in a comma-constructed sequence. Are
> *all* nodes in
> > the sequence below in document order, or is the final
> node-sequence (before
> > applying the predicate) the result of concatenating all
> <salary/> nodes in
> > document order, followed separately by all <bonus/> nodes in
> document order?
> >
> > >   (salary, bonus)[. > 0]
> >
> > Howard
> >
> > > -----Original Message-----
> > > From: www-ql-request@w3.org [mailto:www-ql-request@w3.org]On Behalf Of
> > > Kay, Michael
> > > Sent: Tuesday, January 07, 2003 7:00 AM
> > > To: Howard Katz; www-ql@w3.org
> > > Subject: RE: meaning of (salary, bonus)
> > > >
> > > >      (salary, bonus)
> > > >
> > > > with the following commentary: "This expression contains all
> > > > salary children of the context node followed by all bonus children"
> > > >
> > > > Can this expression be used outside a location path? I can
> > > > see returning this expression as a function result, but can
> > > > someone provide other examples of valid use? And in such a
> > > > case, what is the meaning of "context node"?
> > > >
> > >
> > > Sure, the expression can be used anywhere, for example
> > >
> > >   fn:average((salary, bonus))
> > >
> > > returns the average of this sequence - in this case it's
> actually the same
> > > as
> > >
> > >   fn:average(salary | bonus)
> > >
> > > Or you could write:
> > >
> > >   (salary, bonus)[. > 0]
> > >
> > > to exclude the values that are negative.
> > >
> > > In fact, writing the expression within a location path is one
> of the least
> > > useful places to use it, since the results of a path
> expression are always
> > > in document order. So person/(salary,bonus) actually returns the
> > > same result
> > > as person/(salary|bonus).
> > >
> > > The "context node" is exactly what it would be if you wrote
> the expression
> > > "salary" instead of "(salary, bonus)".
> > >
> > > Another common use case is when building a sequence recursively:
> > >
> > > <xsl:function name="reverse">
> > >   <xsl:param name="p"/>
> > >   <xsl:result select="if ($p)
> > >                       then (reverse($p[position()!=1]), $p[1])
> > >                       else ()"/>
> > > </xsl:function>
> > >
> > >
> > > Michael Kay
> > >
> >
> --
> Mary Fernandez, Principal Technical Staff Member
> AT&T Labs - Research, 180 Park Ave., Room E243, Florham Park, NJ
> 07932-0971
> phone: 973-360-8679,  fax: 973-360-8187
> mff@research.att.com, http://www.research.att.com/~mff
>
>
Received on Tuesday, 7 January 2003 23:39:22 GMT

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