Stringly is everything defined in https://www.w3.org/TR/sparql11-query/#func-strings
In other words it is a simple literal, a plain literal with language tag, or a literal with datatype xsd:string
In other words, since utils-expression-evaluator transforms a simple literal to xsd_string.
It is RDF_LANG_STRING or XSD_STRING.
Reasons for this are mentioned here: w3c/sparql-12#112
Stringly is everything defined in https://www.w3.org/TR/sparql11-query/#func-strings In other words it is a simple literal, a plain literal with language tag, or a literal with datatype xsd:string In other words, since utils-expression-evaluator transforms a simple literal to xsd_string. It is RDF_LANG_STRING or XSD_STRING. Reasons for this are mentioned here: w3c/sparql-12#112