CWM (Closed World Machine) extension. Adds support to "python://" URIs, as a way to call arbitrary python functions as if they were built-ins.

When a URI like python://mymodule#myfunction is found in a rule, it imports the module and uses the function as a built-in.

Example: teste.n3:

:c :input ("All these worlds are yours except europa") .

{?x :input (?y).
    ?z1b <python://#unicode.upper> (?y) .
    ?z2 <python://#unicode.rsplit> ( ?z1b " " 2 ) .
}=>{
    ?x :output ?z2.
}.

cwm_py teste.n3 --think --data

 @prefix : <#> .

:c     :input  (
    "All these worlds are yours except europa" );
     :output  (
    "ALL THESE WORLDS ARE YOURS"
    "EXCEPT"
    "EUROPA" ) .

The equivalent python code would be y.upper.rsplit(" ", 2)

Another example, a little more useful, would be to put a custom function in a file, like teste.py and use that function as a built-in:

teste.py:

import subprocess
def callExt(*arglist):
    return subprocess.Popen(arglist,stdout=subprocess.PIPE).communicate()[0]

teste.n3:

@prefix teste: <python://teste#>.
:d :input ().
{?x :input ().
    ?z1 teste:callExt ("ls" "-l" "../") .
}=>{
    ?x :output ?z1.
}.

cwm_py teste.n3 --think --data

 @prefix : <#> .

:d     :input ();
     :output """total 16
drwxrwxr-x  2 atila.alr atila.alr  4096 Mai  9 08:52 CVS
drwxrwxr-x 26 atila.alr atila.alr 12288 Mai 17 17:54 swap
""" .

To "install" the extension, it should suffice to put cwm_py in the cwm folder. Then, to use it, call cwm_py like you would call cwm. Internally, all the extension does is to monkeypatch an internal function (so it understand "python://" URI) and then pass the ball to cwm.

Sure, the idea of call any function is not very production-security-friendly, but it may come handy in a controlled environment.