Natural language & AI
The 15th International Semantic Web Conference (ISWC 2016), Kobe, Japan
The SPARQL 1.1 Query Language permits patterns inside FILTER
expressions using the EXISTS construct, specified by using substitution.
Substitution destroys some of the aspects of SPARQL that make
it suitable as a data access language. As well, substitution causes
problems in the SPARQL algebra and produces counterintuitive results.
Fixing the problems with EXISTS is best done with a completely different
definition that does not use substitution at all.