Nanopublication SPARQL templates use an extended version of the grlc syntax.

grlc templates use variable names starting with "_" to denote placeholders. Those that end in "_iri" like "?_resource_iri" are IRI placeholder; otherwise they are literal placeholders, like "?_name".

Optional placeholders in grlc, which don't necessarily need to be filled before running the query, start with two underscores instead of just one, e.g. "?__filter_iri" or "?__filtertext".

Nanopublication query templates extend grlc by supporting placeholders that can have more than one value. Those have the suffix of "_multi_iri" (for IRIs) or just "_multi" (for literals). Importantly, they only work if there is at least one occurrence of a "values" statement like "values ?_resource_multi_iri {}", which indicates where the values are filled in. These multi-value placeholders take 1 or more IRIs/literals.

This feature can be combined with optional placeholders, starting with two underscores like "?__resource_multi_iri", which can be filled with zero or more IRIs/literals.