The high-level brief was to produce an implementation conforming to ISO/IEC 19757-3:2020. Conformance is defined in Clause 7 of the standard. What it terms simple conformance amounts to reporting whether an XML document is valid to a given Schematron schema: a simple pass/fail, with SVRL^[33] output not required. Full conformance is also defined, but does not expand much on that, adding as criteria correct attribute values and a proscription on duplicate variable names; SVRL is not mandated here either.^[34] To meet perhaps most users' expectations, align with SchXslt, as well as provide the means to compare outputs with that tool's, SVRL was deemed a necessity from the start; text output is out of scope.

An additional reason for choosing XQuery was the appeal of relatively rapid development facilitated by its concise and declarative syntax.