Re: Parameters

On Fri, Feb 21, 2014 at 10:15 AM, Toman, Vojtech <vojtech.toman@emc.com> wrote:
>
> I see. But suppose your pipeline depends on a number of 3rd-party pipelines where each one uses its own (documented or not) parameter convention internally.
>
> 1. If two of these 3rd-party libraries happen to use p:parameters('') - or, by coincidence, p:parameters('foo') -, then they will get the same map of parameters. In some cases that may be the desirable behavior, but in general, I am afraid, it is not.
>
> 2. If you take the transitive closure of all the parameter map names used by all the nested/imported pipelines, wouldn't it effectively mean that the poor user would have to specify values for each of these maps on the command-line? But the user cannot know what the parameter map names are, as this is not obvious from the main pipeline.
>
> Given that you have no control over the 3rd-party pipelines/libraries, I am worried that this may lead to completely unmaintainable mess.

I'm not certain how this is any different than today.  When you invoke
someone's step, you can explicitly bind the parameters to whatever
you'd like.  If they have internally used specific named sets of
parameters without exposing control over that via an option, their
library wouldn't be that usable.

Thinking that through:

Suppose someone had a pipeline with an XSLT step and they've packaged
that for reuse as a step.  The XSLT step doesn't do anything with the
parameters option and so they get the default value which binds the
option to p:parameters('').

Now, someone uses that step within their pipeline and they set some
parameters on invocation.  Those parameters will be used by the XSLT
within the imported step.

Is this a good thing?  It depends on what you are doing.  If that XSLT
is complicated (e.g. the docbook stylesheets) and has many, many
parameters, being able to pass particular parameters to the XSLT step
contained in the imported pipeline easily is a good thing.  On the
other hand, if it causes the contained XSLT to do the wrong thing,
that is a bad thing.

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics

Received on Friday, 21 February 2014 10:26:40 UTC