Circular dependencies

https://www.w3.org/community/xformsusers/wiki/XForms_2.0#The_xforms-recalculate_Event

"All computes that directly refer to an instance node are its dependants;  
excluded are references to the current node's value in calculate  
expressions (such an instance node does not take itself as a dependent).

A compute is computationally dependent on an instance node if there is a  
path of dependants leading from the instance node through zero or more  
other instance nodes to the compute.

A compute is part of a circular dependency if it is computationally  
dependent on itself.

...

If a compute is computationally dependent on an element in L and part of a  
circular dependency, then an xforms-compute-error event must be dispatched  
to the model element."

According to these definitions, it seems like

	<bind ref="a" constraint=". != 13">

is a circular dependency.

Steven