create a rule in programming

Business Rule Definition is stored as XML in XData block named RuleDefinition inside rule class and can be (de)serialized as an object of Ens.Rule.Model.ruleDefinition class. Some utility methods are available there.

Here's an example of modifying Demo.ComplexMap.Rule.SemesterBatchRouting rule in ENSDEMO class. It modifies "when" condition from 1 to 0.

zn "ENSDEMO"
set ruleClass = "Demo.ComplexMap.Rule.SemesterBatchRouting"
set sc = ##class(Ens.Rule.Model.ruleDefinition).LoadFromClass(ruleClass, .rule)
set rule.ruleSets.GetAt(1).actions.GetAt(1).whens.GetAt(1).condition=0
w rule.SaveAs(ruleClass)
set sc=$system.OBJ.Compile(ruleClass,"k-d")

But instead of:

set sc = ##class(Ens.Rule.Model.ruleDefinition).LoadFromClass(ruleClass, .rule)

You need to create and fill rule object manually.

Relevant discussion.