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Re: p:exec -- can it apply to only selected parts of input using a loop?

From: Alex Muir <alex.g.muir@gmail.com>
Date: Mon, 7 Feb 2011 19:38:13 +0000
Message-ID: <AANLkTi=nC2GT50X_SeLwHmVwtmOeEbDst20uzs88r9Ag@mail.gmail.com>
To: Leif Warner <abimelech@gmail.com>
Cc: XProc Dev <xproc-dev@w3.org>
Yeah and the subpipeline lets you do anything within that operation that
could affect other things not within the xml result file such as some
http-request to another server to initiate an operation.

I have been thinking of xml for document processing only these days however
pipelines are used in industry to communicate results of some data analysis
on data that just came into a company for example and could literally send a
message about the data and transform it into some other information for
example which is a ticket to say I have processed this input data and save
that in the xml node with a copy of the input which is moved to database by
another pipeline. So viewport now does sound more appropriate in that
context given one is viewing some data and porting a bunch of information to
other severs.. lol

I may be it's more often about doing something with the data rather than say
document standardization for example. Although both are possible domains of
xproc. These days,, months,, I'm just standardizing data so have been
thinking of the pipeline as a means to organize a series of xslt
transformations and viewport is hardly a natural term in that context. In
that context it's more like a p:doEdit ;)

Can't please every newbie..

On Sun, Feb 6, 2011 at 10:09 PM, Leif Warner <abimelech@gmail.com> wrote:

> I think of p:viewport as the counterpart to p:for-each that doesn't split
> up the input into a sequence of documents.  I think of it like the "map"
> function in most languages - apply an operation to a sequence but don't
> modify the structure.
> The name was a big stumbling block for me as to what it's actually for when
> I first got started.
> I would prefer a name like "map" or at least something that more strongly
> ties it to p:for-each.
> (I know languages like Ruby, Python, JavaScript, and Scala have both map
> and foreach counterparts.  And then languages like Haskell, XQuery, and XSLT
> don't differentiate between the two as they're functional/declarative
> languages.)
> -Leif Warner
> On Sat, Feb 5, 2011 at 4:09 AM, Alex Muir <alex.g.muir@gmail.com> wrote:
>> Sorry if I was a bit annoying on this posting but I found the discussion
>> instructive and the emotion I was trying to convey from the keyboard was one
>> of positive inquisitive criticism. I had some more thoughts on this which
>> led to some observations.
>> Jostein opened my eyes to the fact that viewport is more a for-each-match
>> than a modify nodes.
>> The thought came to mind that this common xslt pattern could be thought of
>> as a viewport in some way.
>> <xsl:template match="*">
>>     <xsl:copy>
>>       <xsl:copy-of select="@*"/>
>>       <xsl:apply-templates/>
>>     </xsl:copy>
>>   </xsl:template>
>> <xsl:template match="some/path">
>>   ...
>> </xsl:template>
>> I studied more about the difference between for-each and viewport in the
>> spec.
>> I noted from the spec that one important difference is that for-each can
>> apply to a "sequence of documents" and viewport applies to a "single
>> document" both "applying its subpipeline to one or more subtrees".
>> I had not yet seen an example applying for-each to a sequence of documents
>> as it's input but would like to see one. Rather the examples I have seen are
>> all applying a for-each to one input document like a directory list and say
>> outputting a sequence of documents.
>> I note the spec says when describing p:iteration-position "Both p:for-each
>> and p:viewport process a sequence of documents."
>> and that
>> "Within a p:viewport, the p:iteration-position and p:iteration-size are
>> taken from the sequence of documents that will be processed by the
>> p:viewport. The total number of documents is the p:iteration-size; the
>> ordinal value of the current document (the document appearing on the current
>> port) is the p:iteration-position.?"
>> So I'm wondering what is being conveyed by the descriptions regarding
>> viewport as working with a sequence of documents or single documents. Is
>> this a contradiction or is there a reason the spec speaks of sequences of
>> documents and a single document with relation to viewport?
>> Regards
>> Alex
>> On Wed, Feb 2, 2011 at 1:14 PM, Jostein Austvik Jacobsen <
>> josteinaj@gmail.com> wrote:
>>> Also, viewports are useful for other stuff than just modifying a
>>> document.
>>> For instance, what if you wanted to store all HTML elements as separate
>>> HTML files but ignore all TEXT elements? in this case p:modifySubtree
>>> and p:modifyNode wouldn't be meaningful.
>>> I look at p:viewport as a kind of advanced version of p:for-each. If it
>>> had to be renamed, then maybe p:for-each-match ?
>>> Anyway, I like "p:viewport" - both the step and it's name :)
>>> Regards
>>> p:viewport-fan
>>> 2011/2/2 <vojtech.toman@emc.com>
>>> > Vojtech,, although I understand your points fully they
>>>> > speak to me that viewport is talking about something
>>>> > other than xml documents.
>>>> Yes, the original viewport definition(s) may be unrelated to XML, but
>>>> that does not mean we cannot take existing concepts and apply them to XML,
>>>> or to any other area.
>>>> Regards,
>>>> Viewport :)
>>>> --
>>>> Vojtech Toman
>>>> Consultant Software Engineer
>>>> EMC | Information Intelligence Group
>>>> vojtech.toman@emc.com
>>>> http://developer.emc.com/xmltech
>> --
>> Alex
>> -----
>> Currently:
>> Freelance Software Engineer 6+ yrs exp
>>  <http://www.facebook.com/pages/Bafila/125611807494851>
>> Previously:
>> https://sites.google.com/a/utg.edu.gm/alex/
>> A Bafila, is two rivers flowing together as one:
>> http://www.facebook.com/pages/Bafila/125611807494851
>> Working on something like <p:pipe cmd="w3m $input lt $output, errOutput
>> $error"/>

Freelance Software Engineer 6+ yrs exp

A Bafila, is two rivers flowing together as one:
Received on Monday, 7 February 2011 19:38:46 UTC

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