...
Using code should only be used as a last resort and if there is no other choice. Whenever possible backend data should be taken from the business entity. If the data does not exist in the business entity, consider adding the fields or even creating another business entity with just the required fields.
To run simple synchronous code like fetching data from the UI, Corticon.js supports JavaScript functions calls in rulesheets. You can create custom properties and set their values with JavaScript function in the fixed rulesheet.
...