Re: BNODE(string) and joins

I’ve provided an example in the conversation with Rob Vesse: https://lists.w3.org/Archives/Public/public-sparql-dev/2018OctDec/0002.html

Meanwhile, I’ve implemented Rob’s interpretation, although it goes against my intuition about the semantics of solution mappings of which I thought as representing possible truthy interpretations of basic graph patterns, so I wouldn’t have thought that the merge of a join introduces a new solution mapping: https://lists.w3.org/Archives/Public/public-sparql-dev/2018OctDec/0003.html


> On 8. Oct 2018, at 14:53, Axel Polleres <axel.polleres@wu.ac.at> wrote:
> 
> Not 100% sure I understand the question,could you maybe provide a concrete example?
> You are right , that implementations shall generate two different blank nodes on each bnode(s) call with the same string.
> Once they are created, e.g. in a bind, further up in joins these should behave as any other bnodes. 
> --
> Dr. Axel Polleres 
> url: http://www.polleres.net/ <http://www.polleres.net/>  twitter: @AxelPolleres
> 
>> On 04.10.2018, at 23:39, Marcel Otto <marcelotto.de@googlemail.com <mailto:marcelotto.de@googlemail.com>> wrote:
>> 
>> Hi,
>> 
>> I'm implementing a SPARQL engine in Elixir ([1], [2]). Currently, I'm implementing the interpretation of group graph patterns and have the following question an the handling of blank nodes generated with `BNODE(string)`. When performing the merge of two solutions for a `join`, which of the two merged solutions should the merged solution be based on with respect to `BNODE(string)`? For example, let's say I have two sub groups using the `BNODE(string)` function to generate bnodes for the same string, which would result due to the locality of the `BNODE` function different bnodes. So, when the `BNODE` function is now called in the outer group above the two subgroups, again with the same string, what bnode should be returned? 
>> 
>> Kind regards,
>> Marcel Otto
>> 
>> [1] https://github.com/marcelotto/sparql-ex <https://github.com/marcelotto/sparql-ex>
>> [2] https://lists.w3.org/Archives/Public/public-lod/2018Sep/att-0035/00-part <https://lists.w3.org/Archives/Public/public-lod/2018Sep/att-0035/00-part> - announcement about the whole project on the public-lod mailing list
>