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Re: [DTB] What is a dialect?

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Fri, 10 Apr 2009 16:12:12 +0200
Message-ID: <49DF53BC.1010602@inf.unibz.it>
To: Axel Polleres <axel.polleres@deri.org>
CC: RIF <public-rif-wg@w3.org>
The places where the use of the word "supported" is really problematic
is in the definitions of "literalNotIdentical" and "isLiteral(Not)OfType".
But I expect that these definitions will be awkward, even if "supported"
is defined, because they seem to change depending on the dialect at
hand.  This would violate our requirements on extensibility.

The problem is easily solved for isLiteral(Not)OfType, once we define
how types are represented (the second argument in the domain is
restricted to the set of data types, i.e., all datatypes that have
existed, currently exist, and will exist in the world), and it becomes a
nonissue if we adopt my proposal [1] and revert back to individual guard
predicates.

literalNotIdentical is trickier. Basically, the problem is that BLD does
not make a distinction between the datatype part of the domain and the
rest. So, the domain of a given interpretation can contain some values
from the value space of some datatype that is not in DTS. This situation
can be remedied by adding to the definition of semantic structures the
assumption that the domain does not contain any values of the value
space of any datatype that is not in DTS.
In that case, one can simply define:
Itruth  ╬┐Iexternal( ?arg1  ?arg2; pred:literalNotIdentical( ?arg1 ?arg2
) )(s1 s2) = t if and only if s1 and s2 are in the value spaces of some
datatypes and s1 neq s2.
(I did not understand what you mean with "point in a space")


Best, Jos

[1] http://lists.w3.org/Archives/Public/public-rif-wg/2009Apr/0030.html

Axel Polleres wrote:
> Jos de Bruijn wrote:
>> What is a dialect? And what does it mean for a dialect to support a
>> datatype?
>>
>> This is not defined in DTB, but it is referred to very often. 
> 
> Yes, and I firmly believe that a definition of what is a dialect does
> not belong into DTB
> 
> It is somewhat defined in FLD (but not spelled out as definition of
> "what is a dialect") in the following sense:
> 
> FLD, Section 3.3:
> "Semantic structures are always defined with respect to a particular set
> of datatypes, denoted by DTS. In a concrete dialect, DTS always includes
> the datatypes supported by that dialect. All RIF dialects must support
> the primitive datatypes that are listed in Section Datatypes of [RIF-DTB]."
> 
> That is a datatype is supported by a (logic) dialect, if it is a member
> of DTS in the semantic structures for that dialect.
> 
>> In
>> particular, what happens if I use a dialect (e.g., BLD), but use more
>> datatypes than are strictly required to be supported by implementations?
>> In addition, it is nowhere specified which datatypes are "supported" by
>> Core or BLD.
> 
> The semantics of BLD is defined in terms of DTS, but indeed the BLD
> document doesn't fix DTS to only those mentioned in DTB, see BLD,
> Section 3.2, it is only said that:
> 
> "The effect of datatypes. The set DTS must include the datatypes
> described in Section Primitive Datatypes of [RIF-DTB]. "
> 
> 
> In what is quoted above from FLD and BLD, it is implicit that ALL
> dialects must support those DTs in DTB. but it might not be said that
> they do not support more. Still, DTB is not the place to define this, is
> it?
> 
> Apart from supported datatypes, FLD specifies, and DTB relies on this
> (copying the definitions in an appendix, which, re-thinking it, is not
> such a brilliant idea) that a dialect defines a Coherent set of external
> schemas, DTB defines exactly such a set of coherent schemata.
> 
> 
> We probably should spell this out in DTB or FLD:
> 
> A RIF dialect needs to define:
>  - a set of supported symbol spaces
>  - a subset of symbol spaces with a special semantics which are the
> supported primitive datatypes
>  - a coherent set of external schemata, defining external functions and
> predicates.
> 
> Still, even this doesn't define what a dialect IS, does it?
> And, does this only apply to logic dialects, does it also apply to PRD?
> etc. I have not answer at this point to this and would appreciate
> opinions how to address this in DTB.
> 
> 
> Axel
> 
> 

-- 
+43 1 58801 18470        debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
----------------------------------------------
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  - Thomas Fuller
Received on Friday, 10 April 2009 14:13:04 GMT

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