YASQE flags correct path syntax as inccorrect

[wouterbeek]

YASQE flags correct path syntax inside blank node abbreviation forms as incorrect.

MWE:

prefix : <http://>
select * { :s :p1 :o1 ; :p2 [ :p3/:p4 :o2 ] }

This is correct according to sparql.org and according to the W3C BNF grammar.

[LaurensRietveld]

Pff, horrible, the sparql grammar. Postponing this for now, and will look into it later.

ps. interestingly enough, the other js SPARQL parsers fails on this query specifically as well: https://github.com/RubenVerborgh/SPARQL.js

[wouterbeek]

@LaurensRietveld SPARQL syntax not that bad (compared to GML syntax, that is :-P), let me walk you through it:

First, we use the following rule to introduce an anonymous blank node with square bracket notation:

[101] BlankNodePropertyListPath ::= '[' PropertyListPathNotEmpty ']'

Within the brackets we are then allowed to write a VerbPath followed by an ObjectListPath:

[83]  PropertyListPathNotEmpty  ::= ( VerbPath | VerbSimple ) ObjectListPath
                                    ( ';' ( ( VerbPath | VerbSimple ) ObjectList )? )*

For the VerbPath we can quickly walk through a sequence of simple grammar rules that show us that iri '/' iri is legal:

[84] VerbPath         ::= Path
[88] Path             ::= PathAlternative
[89] PathAlternative  ::= PathSequence ( '|' PathSequence )*
[90] PathSequence     ::= PathEltOrInverse ( '/' PathEltOrInverse )*
[92] PathEltOrInverse ::= PathElt | '^' PathElt
[91] PathElt          ::= PathPrimary PathMod?
[94] PathPrimary      ::= iri | 'a' | '!' PathNegatedPropertySet | '(' Path ')'

The ObjectListPath is a simple iri.

[LaurensRietveld]

It seems the YASGUI grammar is correct (and the only sparql.org validator isnt ;)). Your clause [ :p3/:p4 o2] is incorrect. Paths are not allowed there (see https://www.w3.org/TR/sparql11-query/#rPropertyListPathNotEmpty), only ObjectLists