[Versa] Issue 1, better literal and datatype support

[Michael Olson]

>>
>> I had exactly the same suggestion.  So your suggestion a literal
>> datatype as a *replacement* for strings and numbers?  If so, I'd
>> agree, since that would completely cover all literals (especially if
>> we include the capablity to associate xsd - or other - datatypes to
>> the underlying model) and would be more inline with RDF Literals.
>
> I don't know.  I think that would suck in syntactic terms.  In cases
> such as
>
> length($mylist, 1)
>
> That 1 is more at the Versa layer, and I don't think it should be
> changed to
>
> length($mylist, "1"^^xsd:int)
>

Why.  We convert plain strings to numbers according to section 3.  Why  
not a typed literal?

>
>> Specifically:
>>
>> uuu aaa lll (where lll is a plain literal (with or without a language  
>> tag)
>>
>> implies
>>
>>  _:nnn rdf:type rdfs:Literal .
>>
>> where _:nnn identifies a blank node allocated to lll by rule rule lg.
>>
>> So, the literals themselves are thought of as resources by the RDF
>> model (especially if they are typed)
>
> Did the latest RDF specs really do that?  That's really bloody messy.
> So to what extent do these magic blank nodes confer identity on
> (previously identified) literals?

You should read the spec.  There is equiality between literals.  It  
also depends on the level os support the model has.  But it is valid to  
have two statements pointing to the same literal blank node.


>   To what extent does this bloat the
> model?
>

It actually helps in so many ways (having just implemented it).  Both  
in model size (now a statements table only needs three columns not  
four), interfaces, no more addStatement for literals and addStatement  
for resources, queries, etc.  I think it is a very smart move.

> Oh yeah.  The spec says "These rules allow blank nodes to proliferate,
> producing highly non-lean graphs".  Nice euphemism.  Bah.
>

I have no issues with this statement except it might not belong in a  
specification.

Isn't it where we went with 4RDF at one time?  a literals table with a  
foreign key from the statement table to the literal table.  exact same  
concept...

> BTW, You mentioned language specifiers.  I think we should add those as
> well, while we're on data types.

Yep

BTW, can someone fix the reply-to on this list so we don't continually  
get 2 copies of the message.

Thanks
Mike

>

------------------------------------------------------------------------ 
-----------------
Mike Olson                                                Principal  
Consultant
mike.olson at fourthought.com                +1 720 253 4662
Fourthought, Inc.                                       
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PO Box 270590,                                       http://4Suite.org
Louisville, CO 80027-5009, USA
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