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XProc 3.0: Automatically connect primary ports passing sec output steps; sink/identity as an attribute on steps

From: Jan Pertermann <j.pertermann@srz.de>
Date: Sun, 25 Feb 2018 13:42:02 +0100
To: xproc-dev@w3.org
Message-ID: <000001d3ae36$09555290$1bfff7b0$@srz.de>
Hi,

first, many thanks to the team working on XProc 3.0 and also for your
insights at XML Prague!

I have three proposals which I am not sure about, if they could work and
also if that has been a topic in the past:

(1) Consider you need to connect a primary output port from step "p1" to a
following step "p2" that has a primary input port. In between these steps
you have one or more steps, that don't have a primary output port.

Wouldn't it be consequent to automatically connect the primary input/output
ports? Because it is obvious, that "p2" cannot connect to a preceding step
with no primary output, isn't it? That could save some lines of code
defining explicit connections and it keeps the pipeline readable. On the
other hand, I have the feeling, that this is a misconception and leads to
confusion when trying to understand a pipeline; and break things for
implementers :-)

Example 1:
---
<p:identity name="p1">
    <p:with-input port="source">
        <c:result>Hello World!</c:result>
    </p:with-input>
</p:identity>

<p:store name="s1" href="test1.xml"/>

<p:store name="s2" href="test2.xml"/>

<p:add-attribute name="p2" match="/*" attribute-name="type"
attribute-value="test"/>

<p:store name="s3" href="test3.xml"/>
---

The output of "s2" gets the same as that of "s1". The output of "s3" gets
<c:result type="test">Hello World!</c:result>.


(2) Secondly, I could imagine to have an attribute @sink="false|true" on any
step as an alternative to <p:sink>. That would allow me to prevent passing
the primary output from "p1" to the following steps in a simple way (by
adding it to itself). Or it would allow me to prevent the implicit sink on a
step without primary output.

Example 2:
---
<p:identity name="p1">
    <p:with-input port="source">
        <c:result>Hello World!</c:result>
    </p:with-input>
</p:identity>

<p:store name="s1" href="test1.xml" sink="false"/>

<p:store name="s2" href="test2.xml" sink="false"/>

<p:add-attribute name="p2" match="/*" attribute-name="type"
attribute-value="test"/>

<p:store name="s3" href="test3.xml" sink="false"/>
---


(3) A contrary approach is an attribute @identity="false|true" allowing to
pass through the primary input without changes.

Example 3:
---
<p:identity name="p1">
    <p:with-input port="source">
        <c:result>Hello World!</c:result>
    </p:with-input>
</p:identity>

<p:store name="s1" href="test1.xml" identity="true"/>

<p:store name="s2" href="test2.xml" identity="true"/>

<p:add-attribute name="p2" match="/*" attribute-name="type"
attribute-value="test"/>

<p:store name="s3" href="test3.xml" identity="true"/>
---


(1) may be unorthodox, but (2) and (3) could help a lot to keep pipelines
readable without changing the current spec too much. What do you think about
it?

	
Regards,
Jan


-- 
Jan Pertermann, Dipl.-Ing (FH)
XML-Applikationsentwickler

SRZ Berlin
http://www.srz.de
Received on Sunday, 25 February 2018 12:43:06 UTC

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