Re: On the inevitability of SPARQL/SPIN for SHAQL

On 3/3/2015 15:30, Jose Emilio Labra Gayo wrote:
> On Tue, Mar 3, 2015 at 6:11 AM, Holger Knublauch 
> <holger@topquadrant.com <mailto:holger@topquadrant.com>> wrote:
>
>     On 3/3/2015 14:59, Jose Emilio Labra Gayo wrote:
>>
>>
>>         Why should this group take on such undertaking instead of
>>         reusing already existing language produced by W3C?
>>
>>
>>     Because "SPARQL queries cannot easily be inspected and
>>     understood, either by human beings or by machines, to uncover the
>>     constraints that are to be respected". [1]
>
>     Jose, the sentence following your excerpt above is
>
>     "The term 'shape' emerged as a popular label for these constraints."
>
>     I believe this clarifies that the group was not contrasting SPARQL
>     with something like XPath,
>
>
> Not at all...why do you say that?

Because you were responding to Irene's question that was comparing 
SPARQL with your XPath variant. The quote that you used to defend your 
view point was about something else.

>
> I think I have already clarified what subset of XPath I was talking 
> about and for what purpose.
>
>     but rather SPARQL versus the high-level vocabulary of sh:minCount
>     and sh:valueType. A new language such as a yet-to-be-defined
>     variant of XPath or a yet-to-be-defined subset of SPARQL's FILTER
>     expressions would arguably have the same basic characteristics as
>     SPARQL itself.
>
>
> No, because that subset of XPath (or SPARQL expressions as Richard 
> said) can be used for built-in functions and operations and has a much 
> simpler semantics that we can leverage on than the full SPARQL 
> language with BGPs, UNIONs, OPTIONALs, etc.

SPARQL expressions include EXISTS and NOT EXISTS [1], i.e. you would 
need to define a sub-set of SPARQL expressions here to avoid the 
features you describe.

Sorry, I am not seeing any realistic support for defining such a new 
language for SHACL. It would exclude too many real-world use cases. Your 
goal of "simple semantics" has not been approved, and I don't believe it 
should be approved because it limits the usefulness of the language. As 
Richard stated, such a reduced language would fail on the marketplace.

Holger

[1] http://www.w3.org/TR/sparql11-query/#func-filter-exists