changes to Proposal B

On 03/23/2017 08:11 AM, Andy Seaborne wrote:
> https://w3c.github.io/sparql-exists/docs/sparql-exists.html
> 
> I've made some updates to reflect recent discussions and also to add
> descriptive text.  What I'd really like feedback on is where less can be
> said.  Just adding text to explain points risks putting too much in.
> 
>     Andy
> 


I see that the domain of PrjMap has been expanded.  This doesn't affect EXISTS
because the argument to EXISTS can't result in a projection (because internal
projections are always inside a ToMultiSet).

There appears to have been some changes to the section on limitations on
assignment.  This section is still quite unclear.  I guess that it means that
there cannot be an AS binding to the variables coming from outside anywhere in
the argument to EXISTS.  This is far too broad, as it prevents AS binding of
disconnected variables of the same name.  It also prevents AS binding in
places that are non-problematic, such as AS binding in the select clause.

There also appears to be a requirement that VALUES not use variables coming in
from the outside.  I don't see any particular need for this limitation.  It
may be that this is in response to a problem that I pointed out where the
example used such a VALUES construct, but the problem has nothing to do with
assignment and instead has to do with there not being a place in the resultant
algebra where values insertion takes place.

Proposal B adds in a new kind of technology to SPARQL, namely replacement of
variables by fresh variables.  This new technology needs to be carefully
examined before it becomes a part of SPARQL.  A detailed explanation of it is
needed, including demonstration of its safety, so that this examination can be
done effectively.

Peter F. Patel-Schneider
Nuance Communications

Received on Friday, 31 March 2017 14:19:06 UTC