RFE to the XForms API - Archive of obsolete content
for example, every visual xforms element exposes the nsixformsdelegate interface.
...as an example, the nsixformsaccessors interface which allows a user to get/set the value of an instance node and get the state of an instance node, is exposed by the nsixformsdelegate interface using the accessors property.

XForms API Reference - Archive of obsolete content
ol nsixformsns...element interfaces extending xforms specification interfaces nsixforms...uielement interfaces implemented by the js part of a control nsixforms...accessors interface exposing states about the bound instance node for a given control frozen interfaces nsixformsmodelelement the model interface experimental interfaces nsixformsdelegate the delegate interface for xforms:custom_controls nsixformsaccessors the accessors interface for xforms:custom_controls nsixformsnsmodelelement custom extension(s) to the nsixformsmodelelement interface nsixformsnsinstanceelement custom extension(s) to the instance element ...

RFE to the Custom Controls Interfaces - Archive of obsolete content
in short, we have the following interfaces: nsixformsaccessors - serves to get/set the value of the instance data node that the xforms element is bound to as well as getting the various states of that node nsixformsdelegate - used to obtain the nsixformsaccessors interface nsixformsuiwidget - used by the xforms processor to update the value/state of an xforms element when its bound node's value/state is changed our current mechanism that allows authors to build custom controls assumes that the controls will be bound to instance nodes of simple content type.