extension namespaces for p:system-property() names

Gentlefolk,

 

The p:system-property() function allows for implementations to support
properties with names in a non xproc namespace.

 

<p:log> supports use-when attribute, but use-when requires an xpath
expression that can be evaluated statically - which makes it difficult to
turn <p:log> on/off on a run by run basis without changing pipeline source
code.

 

If we (http://exproc.org/ ) defined the following two (proposed) extension
namespaces then complying implementations would provide a simple way to
control logging with use-when attribute 

 

1)       a namespace for use with p:system-property() to represent the
current environment variables (a notion reasonably consistent across most
operating systems)

 

Suggested name:    http://exproc.org/proposed/ns/properties/env

Suggested normal prefix: env

Example use: <p:log href='.' use-when="p:system-property('env:logall')" />

 

2)       a namespace for use with p:system-property() to represent the
properties of the runtime process - specifically to access
java.lang.System.getProperty() for java based implementations but for use as
appropriate on other platforms (someone more familiar with such
implementations could define more exact semantics here)

 

Suggested name:    http://exproc.org/proposed/ns/properties/runtime

Suggested normal prefix: rt

Example use: <p:log href='.' use-when="p:system-property('rt:log-detail')
&gt; 4" />

 

 

Of course these could also be useful outside of <p:log use-when= 

 

As an aside, xproc provides a way to query for the existence of extension
steps (  p:step-available() ) but does not provide a way to check whether
p:system-property() supports a particular extension namespace.  Should there
be a standard function to check for p:system-property extension namespace
support?