The variable is only assigned within a single assign activity and possibly has an initialization expression.

The assign immediately precedes the main activity that uses the variable as input (either in a sequence or through a link).

The assign qualifies to be converted into an XQuery assignment type: There is only one copy expression, the copy has a from expression, which uses XQuery, and there is no initialization expression for the variable.

If the variable is an element type, it is changed to a message type, and all copies that set it get a new "part" attribute.

If the variable was an element type and had an initialization expression, the initialization expression is moved to become the first "copy" in the assign activity.

If the variable is the only thing assigned in the assign statement that sets it, move the entire assign to be in the implicit scope and move all the inbound and outbound links for the assign to the implicit scope (adding to the inbound or outbound links that are already there). Otherwise, move just the copies from the assign to a new assign activity inside the implicit scope.

Move the variable into the implicit scope and rename it (and all of its uses) to "parameters.".

Convert copy "from" constructs to use expressions (unless they are from a literal). from

variable.part

with

query="/foo/bar"

becomes

$parameters.part/foo/bar

, from variable with

property="ns:foo"

becomes

abx.getVariableProperty('parameters','ns:foo')

, copy from

variable.part (query?)

to copy from an expression.