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Re: Directed vs Generic Syntax

From: Alex Milowski <alex@milowski.org>
Date: Thu, 13 Apr 2006 13:03:51 -0700
Message-ID: <443EAEA7.6090304@milowski.org>
To: public-xml-processing-model-wg@w3.org

Norman Walsh wrote:
> / Alex Milowski <alex@milowski.org> was heard to say:
> | Taking the following example from Jeni Tennison's email:
> [...]
> | This means the pipeline compiler needs to understand each directed
> | syntax--including extension steps.  While this adds to the implementors
> | work, I think the end result is far simpler for the user.
> 
> But it makes it much more difficult for a pipeline to contain
> additional elements that can be safely ignored (extensions or
> documentation, for example).
> 
> I don't see any semantic distinction between this:
> 
>   <p:step name="p:xslt">
>     <p:input select="$document" />
>     <p:input name="stylesheet" href="foo.xsl" />
>     <p:output href="result.xml" />
>   </p:step>
> 
> and this:
> 
>   <p:xslt input="$document" stylesheet="foo.xsl"
>           output="result.xml"/>
> 
> except that you've obscured the inputs and outputs from the point of
> view of a reader and you've reduced the number of characters that have
> to be typed a little bit.

I would argue that the 'step' syntax obsures the xslt step far more.

> 
> After some consideration, I think I prefer <p:step name="p:xslt"> to
> <p:xslt> and I am confident that I prefer <p:input> and <p:ouput> over
> attributes. For one thing, it means that I can do this:
> 
>   <p:step name="p:xslt">
>     <p:input name="document">
>       <doc>
>        <p>Some data</p>
>       </doc>
>     </p:input>

Unfortuantely, that doesn't necessary map to more complex steps.

Here are two steps from my tideinfo example service [1][2]:


1. This runs a regular expression on the contents of the XHTML pre
    element:

      <p:regex select="h:pre" pattern=".+" matches="line"/>

2. Similarly, here is a regular expression with a step (a subpipeline)
    the is run on the expression matches:

      <p:regex select="line" pattern="^(\S+)\s+(\S+)\s+(\S+)\s+(\S+)">
        <p:xslt>
           <xsl:transform version="1.0">
           <xsl:param name="group-1"/>
           <xsl:param name="group-2"/>
           <xsl:param name="group-3"/>
           <xsl:param name="group-4"/>
           <xsl:template match="/">
           <xsl:variable name="month" 
select="substring-before($group-1,'/')"/>
           <xsl:variable name="day" 
select="substring-before(substring-after($group-1,'/'),'/')"/>
           <xsl:variable name="year" 
select="substring-after(substring-after($group-1,'/'),'/')"/>

           <t:tide-level date="{$year}-{$month}-{$day}" level="{$group-4}">
              <xsl:choose>
                <xsl:when test="$group-3='EST'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-05:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='EDT'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-04:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='CST'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-06:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='CDT'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-05:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='MST'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-07:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='MDT'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-06:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='PST'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-08:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='PDT'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-07:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='AKST'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-09:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='AKDT'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-08:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='HAST'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-10:00</xsl:attribute>
                </xsl:when>
                <xsl:when test="$group-3='HADT'">
                   <xsl:attribute name="time"><xsl:value-of 
select="$group-2"/>-09:00</xsl:attribute>
                </xsl:when>
                <xsl:otherwise>
                   <xsl:attribute name="time">unknown</xsl:attribute>
                </xsl:otherwise>
              </xsl:choose>
           </t:tide-level>
           </xsl:template>
           </xsl:transform>
        </p:xslt>
      </p:regex>


I think this would get really scary in a generic syntax.

[1] http://www.smallx.com/tideinfo-service
[2] http://www.smallx.com/tideinfo


-- 
--Alex Milowski
Received on Thursday, 13 April 2006 20:04:17 GMT

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