To all XForms gurus here, I am (helping someone in) building an XForms implementation on top of FontoXPath. I see that XForms introduces a bunch of additional useful functions on the default function namespace, such as boolean-from-string() or is-valid-card-number(). [Spec](https://www.w3.org/community/xformsusers/wiki/XForms_2.0#Functions). It also discloses all of the functions in the XPath functions namespace in the xforms namespace.Does anyone know how the other XForms implementations do this? Do they just copy over all of the functions, proxy them in an XQuery module? Reimplement them? All of these seem like a bunch of work, there must be an easier way.