Re: System properties

>>>>> "Colin" == Colin Paul Adams <[email protected]> writes:

>>>>> "Michael" == Michael Kay <[email protected]> writes:
    Michael> Yes, I think it often makes sense to make environment
    Michael> variables accessible as system properties.

    Michael> I'd suggest implementations should provide a command line
    Michael> option "make environment variables available as system
    Michael> properties in namespace X" to give users the best chance
    Michael> of writing portable code,

    Colin> In that case an exslt namespace would be the most portable.
    Colin> E.g.

    Colin> http://exslt.org/environment-variables

Here's a rough specification for it:

Processors that claim support of EXSLT Environment-variables make the
value of an environment variable name XYZ avialable via a call to

system-property (exslt-env:XYZ)

where the prefix exslt-env is bound to the namespace
http://exslt.org/environment-variables 

As usual, any prefix that is bound to this namespace will do - the use
of exslt-env as a prefix is purely illustrative.

The result of the call is dependent purely on the operating
environment. However processors are encouraged to provide an option 
where this system-property call returns the empty string, for security
reasons. This option may be the default behaviour for the processor.

Notes: 

Most (all? - well, Linux at least! :-) operating systems treat 
environment variable names in a case sensitive manner, so users are
cautioned that the local-name is case-sensitive - fortunately this
fits in with the definition of an XML lexical QName.

Normally, you can expect identical results with whatever processor you
use (provided that it claims to support this module, and that the
option is not turned off for security reasons) in a given operating
environment.
Note however, that it is possible that a processor might internally alter the set
of enviroment name-value pairs, just like any other program.
In order to conform to this module, the processor must document any
alterations it makes to the set of name-value pairs in the
environment.
(Maybe it would be nicer to deny conformance in this case, I
think. Opinions?)
Note that if a shell script is used to invoke an XSLT processor, that
shell script might in itself change the set of name-value pairs. 
In this case, no documentation is needed, as this is beyond the
control of the XSLT processor.
-- 
Colin Paul Adams
Preston Lancashire