- From: Andy Seaborne <andy@apache.org>
- Date: Thu, 29 Sep 2016 00:55:10 +0100
- To: public-sparql-exists@w3.org
On 29/09/16 00:44, Andy Seaborne wrote:
> ** Intuition/Outline
>
> Ensure that the variables from the row being filtered are available, not
> just their values as in the spec with substitution.
>
> This is done by restricting the variable to the value of the row at the
> point where the variable is being bound. This is in a BGP. Use of AS
> ?x for ?x in the current row is not allowed : ?x is considered to be
> already set.
>
> ** Proposal
>
> Rewrite the pattern of the EXISTS filter; do this in a deep fashion,
> while respecting scoping rules.
>
> Let V = in-scope variables at the point of the FILTER EXISTS.
>
> For each BGP in the pattern:
> Build a VALUES with variables of V still in-scope at this BGP.
> This includes empty BGPs
>
> Scoping applies.
This process of injection is written differently to the other proposal
but I believe is the same process because EXISTS is evaluated for every
solution mapping at the point of the FILTER. The location of the
injection is different.
Andy
Received on Wednesday, 28 September 2016 23:55:39 UTC