BRE and XML Node Creation

On a recent project, I was tasked with using Business Rules Engine (BRE) to call a list of BRE Policies. These policies could generate a number of results, or triggers, the number of results was not known until runtime. BRE can update existing XML nodes within the Fact document, however, it cannot create nodes that do not already exist.

To solve this issue, I decided to add a serializable .NET object to pass in as a fact. The object has a public method that is used to create trigger objects and add them to the object's collection. Upon return from the BRE call, the raw xml of the object is exposed through it's XmlString property.

First we will talk about the Trigger class. This class represents our result. It is very generic and thus flexible in its use. The TimeStamp field can be used to track the time the trigger was created. We use the InterfaceName field for routing purposes. The Action and SubAction fields can optionally be used to further differentiate the trigger from other triggers during routing. The other section of the Trigger is a collection of Parameters. This is where a list of key-value pairs can be stored for use in processing. We expose a method to add a parameter key-value to the Parameters collection.



The PolicyResults class is a collection of Trigger objects. We expose a CreateTrigger method in order to be able to create Trigger objects on-the-fly from BRE. We also expose two utility properties, Count and XmlString. The Count property returns the number of Trigger objects in the collection. The XmlString property returns the raw XML version of the collection. This property can be loaded into an XmlDocument class and assigned to and XLang message easily.



We use this setup when calling BRE by first creating a PolicyResults object and passing it into BRE as a fact. Next, when creating policies in BRE, we can call the CreateTrigger method in the Assert section of any Rules we create. If the Assert is executed the Trigger(s) will be created and added to our PolicyResults. Once the BRE call is complete we can return the PolicyResults as a string (or XmlDocument) to the calling orchestration, where can be used for processing.