Entailment document: Property Path

A remark concerning the section below :

> 9 Entailment Regimes and Property Paths (Informative)
...
>
> Since property paths are evaluated without entailment, the evaluation 
> under an entailment regime can yield counter-intuitive results. 
> Assuming the use of the RDFS entailment regime and the query
>
> SELECT * WHERE { ?s (ex:p3+) ?o }
>
> over the above given example data, the result is empty. Although the 
> data contains ex:b ex:p2 ex:c and ex:p2 rdfs:subPropertyOf ex:p3, 
> which under RDFS entailment implies ex:b ex:p3 ex:c, this fact is not 
> used since the arbitrary length path expression ex:p+ is evaluated 
> with simple entailment, i.e., via subgraph matching on the input data. 


Some systems may compute and record RDFS entailments before query 
processing occurs. In this case, enumerating ex:p3 edges would return 
entailed edges as well and hence ex:p3+ would have a solution.


Olivier