Optional features
As discussed in the mandatory features of GQL, most optional features are explicitly specified by the Conformance Rules sections in subclauses. In the meantime, a few are specified implicitly elsewhere in the standard. For example, subclause 4.16.8, Immaterial value types: null type and empty type, includes the following statements:
“The immaterial value types are only provided by GQL-implementations that support the Feature GV70, “Immaterial value types”. In such GQL-implementations, the null type provides a portable most specific value type for various values (e.g., certain constructed values such as empty list values or the null value).”
This passage designates the immaterial value types, including null types and empty types, as optional rather than mandatory.
In the ISO/IEC 39075:2024 version of the GQL standard, every optional feature is clearly referenced by a feature ID (formatted as “G” followed by three...
