David,
On 22 Nov 2008, at 14:39, David A. Lee wrote:
I'm a little (ok a LOT) confused between the difference of
'contained steps' and 'subpipeline'
E.g in the spec in this part:
4.1
<p:pipeline
name? = NCName
type? = QName
psvi-required? = boolean
xpath-version? = string
exclude-inline-prefixes? = prefix list>
(p:input |
p:output |
p:option |
p:log |
p:serialization)*,
(p:declare-step |
p:import)*,
subpipeline
</p:pipeline>
What's the difference between the sequence of p:declare-step and
subpipeline ?
It's the same as the difference between the declaration of a function
in your programming language of choice, and the code that makes up the
body of a function. A <p:declare-step> is a declaration of a pipeline
that you can later invoke within the subpipeline. The subpipeline is
the sequence of steps that is performed when the pipeline is called.
What really confuses me is this comment : from 2.1
------
Note
User-defined pipelines (identified with pfx:user-pipeline in the
preceding syntax summary) are atomic. A pipeline declaration may
contain a subpipeline, but the invocation of that pipeline does not.
------
So that last sentance ... is it saying the "subpipeline" in the
above p:pipeline is not executed ?
If so what is done with it ?
This is the same as asking whether the code within a function
definition is executed. It is executed, but only when the function
(pipeline) is invoked. The note you quote is saying that you can't
create user-defined pipelines that hold subpipelines *when you invoke
them*, so you can't create user-defined pipelines that work like the
compound steps <p:for-each>, <p:viewport>, <p:choose> and so on. But
you can create user-defined pipelines that work like the various
atomic steps such as <p:replace> or <p:xslt>.
Does that make any more sense?
Jeni
9 messages in org.w3.xproc-devRe: Difference between 'contained st...
