Re: Naming steps or naming outputs

Norman Walsh wrote:
> Like the question of whether we use <p:step type="xslt"> or <p:xslt>,
> it's on the one hand not technically important which decision we make,
> as I'm sure we can all see that they're essentially isomorphic. And on
> the other, deeply important because it has a dramatic impact on the
> syntax.


I believe a generic syntax (i.e. <p:step type="xslt">) should be chosen
over explicit syntax (i.e. <p:xslt />). Imagine the following scenario:

I have a special purpose component ("my:safeguard") that will check my 
cpu's temperature. If it's below a given threshold (provided by the 
"max-cpu-temp" parameter), it will perform an identity transform. 
Otherwise, an error will be triggered and the pipeline execution will 
fail and stop. This component would prevent me to process a 10GB 
document with my stylesheet (as my cpu would probably melt). The 
corresponding pipeline follows.

<p:pipeline>
   <p:input name="source" />
   <p:output name="result" from="ss.result" />


   <p:step type="my:safeguard" name="sg">
     <p:with-input name="source" from="source" />
     <p:with-param name="max-cpu-temp" value="30ºC" />
   </p:step>

   <p:step type="xslt" name="ss">
     <p:with-input name="stylesheet" uri="http://example.org/foo.xsl" />
     <p:with-input name="source" from="sg.result" />
   </p:step>

</p:pipeline>


If this pipeline was written in a direct syntax, my pipeline processor 
would have to know that an hypothetical <my:safeguard /> tag would 
represent a step. However, if it doesn't recognize it, well... my cpu 
would certainly melt! That wouldn't happen in a generic syntax.

We can imagine all sorts of special purpose components that will behave 
similarly (authentication comes to mind).


As a side bonus, we have an easier GUI tool support for XProc. If I 
develop a GUI that understands steps as blackboxes, I can 
manage/visualize pipelines without caring if they are made of core 
components and/or special purpose ones. With a direct syntax, my GUI has 
to know about each component to be able to support them.

Any thoughts?


Cheers,
Rui