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RE: Execute actions VS external functions

From: Noldus Reijnders <n_reijnders@hotmail.com>
Date: Tue, 19 Jun 2012 15:29:32 +0200
Message-ID: <BAY164-W525E3F41850B6AF28F2B8384FF0@phx.gbl>
To: <csma@fr.ibm.com>, <public-rif-comments@w3.org>

Thank you for your explanation. When I posed the question I thought I could use External as an action, but when better reading the PRD-specification I found out it wasn't. Your explanation makes it more clear!Gr. Noldus
To: n_reijnders@hotmail.com; public-rif-comments@w3.org
Subject: Re: Execute actions VS external functions
From: csma@fr.ibm.com
Date: Tue, 19 Jun 2012 15:22:13 +0200

Hi Noldus,



You wrote on Thu, 24 May 2012 19:12:42
+0200 [1]:

>

> I was wondering how (taken from RIF-PRD specification)

> Do(Execute( act:print(func:concat("New customer:
" _c1)) ))

> differs from ('Do(Execute' changed in 'External')

> External( act:print(func:concat("New customer:
" _c1)) )

> To me it seems they both execute the function.
Could

> someone please explain me the difference between
the two?



The RIF-PRD specification does not allow
External as an action => the proposed alternative conclusion, using
External, is not a well-formed action block in RIF-PRD, and its semantics
are not defined.



This being said, you are right that
Execute is, essentially, the RHS counter-part of Externa. The different
syntax emphasizes the different roles in the semantics of PRD: with External,
a, externally defined function is executed to check whether a substitution
is matching or not; with Execute, it is executed for its side effects only,
and whatever is maps to is discarded.



Cheers,



Christian



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Received on Tuesday, 19 June 2012 13:30:06 GMT

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