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Re: implicit declaration?

From: James Garriss <james@garriss.org>
Date: Wed, 24 Sep 2008 08:10:30 -0400
To: XProc Dev <xproc-dev@w3.org>
Message-ID: <C4FFA676.9EC%james@garriss.org>
Ok, so I'm using wrong terminology; I can work on that.  Thanks for the

Perhaps now I can phrase my question better:  When I look at the declaration
of a step, how do I know if various inputs and outputs are allowed to have
an absent binding and/or an empty binding?

James Garriss

From: Norman Walsh <ndw@nwalsh.com>
Date: Tue, 23 Sep 2008 16:41:01 -0400
To: XProc Dev <xproc-dev@w3.org>
Subject: Re: implicit declaration?
Resent-From: XProc Dev <xproc-dev@w3.org>
Resent-Date: Tue, 23 Sep 2008 20:41:54 +0000

James Garriss <james@garriss.org> writes:

>     <p:identity>
>         <p:input port="source"/>
>     </p:identity>
> is semantically equal to this:
>     <p:identity/>
> Specifically, I can declare the input port explicitly or implicitly.  As I
> read through the WD, what is it that tells me that a port can be declared
> implicitly or must be declared explicitly?  Is it whether it's a primary
> port?

No, you're confusing declaration with use. The declaration for the identity
step is:

   <p:declare-step type="p:identity">
      <p:input port="source" sequence="true"/>
      <p:output port="result" sequence="true"/>

That declaration is given in the spec and is builtin to Calabash
(well, that's not technically true. If you blow apart the jar file,
you'll find it in pipeline-library.xml in /etc).

With the exception of p:declare-step elements, all the steps that you
put in your pipeline documents are *uses* of the steps, not

The fact that an *empty* p:input binding is the same as an *absent*
p:input binding is just a natural consequence of the defaulting for

Does that help?

                                        Be seeing you,

Norman Walsh <ndw@nwalsh.com> | The main difference between living
http://nwalsh.com/            | people and fictitious characters is
                              | that the writer takes great pains to
                              | give the characters coherence and inner
                              | unity, whereas living people may go to
                              | extremes of incoherence because their
                              | physical existence holds them
                              | together.--Hugo Von Hofmannsthal
Received on Wednesday, 24 September 2008 12:11:16 UTC

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