Re: RIF Homework for May 2 Telecon

Hi Michael,
>
> To start the discussion on Paula's doc, here are some comments. All but one
> are hopefully minor and are requests for clarification. Only one is a major
> issue: the requirement for being able to represent an inference system.
> This has already been discussed extensively. I was sitting on the sidelines
> in this discussion, but, in my view, the proponents failed to make their
> case.
>   
Find below some comments on your clarification requests.
>
> 1. Goal
>     CSF 2
>       Requirement 2: Component languages follow same paradigms
>           
> 	  *** Not clear what is meant here.
>   
My idea is to have a uniform framework where a couple of component 
languages (such as a condition language for the body of deductive rules, 
an event language for the E part of ECA rules, and an action language 
for the A part of ECA rules) can be put together for expressing e.g. 
deductive rules or ECA rules. For gaining uniformity and easing RIF's 
design and usage, clear language paradigms should be followed for these 
component languages; which paradigms will be followed is part of the 
solution to meeting this requirement. An example of such a paradigm is a 
pattern-based approach to specifying these languages (as followed e.g in 
Xcerpt and XChange, see http://www.pms.ifi.lmu.de/projekte/xchange); in 
my opinion, it would be better not to mix languages following such a 
paradigm with languages that follow a path-based approach to specifying 
e.g. queris to data (as is the case in XQuery). However, I can imagine 
that RIF will follow a couple of paradigms, which regard different 
aspects of language design or use.
>     CSF 3
>       Requirement 3
>         Desideratum 1: RIF should accept OWL KBs as data
>
> 	  *** Not clear what data is meant here. The A-box?
>   
I think we should enable the use of the T-box too. However, I'm not an 
expert on this and I think the best answer would come from Peter, Jos 
(de Bruijn)  or Jos (De Roo) because they championed this design constraint.
>       Requirement 6: Type system / Datatype built-in predicates and functions
>
>           *** Typing should be optional
>   
Is this referring to RIF Core or RIF in general? Note that at moment my 
hierarchy doesn't make the difference between RIF Core and its 
extensions, but I agree that such a distinction is needed so as to 
understand better what is to be done here.
>
> 2. Goal
>      CSF 1
>        Requirement 2: Format for specifying the inference procedure
> 	     (inference procedure interchange format) that can be applied
> 	     to a set of rules
>
> 	  *** This is very controversial as a requirement. Neither the use
>               cases nor the intent are particularly clear.
> 	      (Where exactly in
>               http://www.w3.org/2005/rules/wg/wiki/Operationally_Equivalent_Translations
> 	      is it needed that an inference procedure should be
>               communicated to another engine?)
> 	      I didn't take part in the previous discussion of this
>               subject, but I do share skepticism that others expressed
>               towards this issue.
>
>   
The mentioned use case explicitly states this requirement; it tries to 
motivate the practical need for preserving operational equivalence 
(''The MITRE-1 use case scenario attempts to explore the consequences of 
using the RIF for translation that attempts to preserve operational 
equivalence.'') However, Requierement 2 refers just to a format for 
specifying this, Requierement 4 for this CSF is  ''Declarative semantics 
as must, operational semantics optional'', which was mentioned also at 
F2F2 in Cannes (e.g. by Francois Bry).
>       CSF 2
>         Requirement 1: Definition of default behavior(s)
>
> 	  *** Not clear what this means.
>   
Sorry for not being clear enough. This requirement refers to rue 
engines' behavior when encountering certain kinds of unsupported 
extensions. This is an abstract way of expressing the conformance stated 
in the charter and the ideas of the design constraint proposed by Christian:
http://www.w3.org/2005/rules/wg/wiki/RIF_must_define_for_all_RIF_elements_a_default_behaviour_for_compliant_applications_that_do_not_know_how_to_process_it

> 3. Goal
>
>     CSF 1
>
>        What is the difference between
>
>           # Desideratum 2: (Scoped) negation as failure is required
> 	  # Desideratum 4: Representation of closed-world assumption for
> 			   rule sets
>
> 	Is #4 implied by #2?
>
>   
This is a good observation, thank you. I will delete Desideratum 4 from 
the list. Btw, this shows that there is still a lot of work to do on the 
proposed hierarchy :)

Thank you for your feedback.

Regards,
Paula