Add DuplicateAccountCheck and CreateAccount Rules

Add DuplicateAccountCheck and CreateAccount Rules
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In this task you create two rules, one called CreateAccount and one called DuplicateAccountCheck. Both rules can fire when a Create event is asserted into the Rete network. However, the DuplicateAccountCheck rule has a higher priority, so it will fire before the CreateAccount rule.

The DuplicateAccountCheck rule checks whether the account identifier provided in the Create event matches the account identifier of any Account instance already in the Rete network. One of the two following situations must occur:

A matching identifier exists in the Rete network: the DuplicateAccountCheck rule prints a message to the console, and consumes — that is, deletes — the Create event. Because that event is consumed, the CreateAccount rule does not fire.
No matching identifier exists in the Rete network: the DuplicateAccountRule rule does nothing, and then the CreateAccount rule fires, and creates the Account concept instance.

What are rules and how are they created? Rules define actions to take when certain conditions are met. Rules are written in the TIBCO BusinessEvents® Extreme rule language, which is similar to the Java language. Rules are declarative and are generally narrow in scope. A rule has three parts: the declaration (declare), the conditions (when), and the actions (then). As with rule functions, you can work in a source view, which displays the Java-like code, or in a form view.

How are rules used at runtime? The rule engine checks all changes and additions to the Rete network and evaluates or reevaluates rules, using their declaration and conditions, as needed. Eligible rules are added to the rule agenda.

What is the rule agenda A rule fires when it is at the top of the agenda. The engine determines the order of firing using rule declarations and conditions, and each rule’s priority and rank (if these features are used). As the contents of the Rete network change, the engine reevaluates rules and removes any that are no longer eligible to fire. See Understanding Conflict Resolution and Run to Completion Cycles in TIBCO BusinessEvents® Extreme Application Architect’s Guide for details.

How can you prioritize rule execution? The Priority setting on a rule is used to determine the order in which rules are fired. Those with a number closer to one fire first. Within a set of rules that have the same priority, a ranking feature enables you to determine which fire before others. The ranking feature uses a callback rule function that enables you to specify business logic to establish the rank of a rule. When there is no reason to force rules to execute in a particular order, leave the Priority and Rank fields set to the default and let the runtime engine determine rule order.

How can you create concept instances? In this task you instantiate an object instance using its ontology function. Another way is using the Instance.createInstance() function. The Instance.createInstance function uses the XSLT mapper to map any of the scope variables (such as properties, attributes and event payloads) to the new instance properties. You can also create event instances in a similar way, using the Event.createEvent() function.


	See Run-time Inferencing Behavior in TIBCO BusinessEvents® Extreme Application Architect’s Guide.

Add the DuplicateAccountCheck Rule

Right click the Rules folder, and select New > Rule.
You see the New Rule Wizard. In the Rule name field, type DuplicateAccountCheck. In the Description field, type Checks for an existing account with the specified identifier. Click Finish.
In the Form tab, set the Priority field to 3. It’s a higher priority than 5, the default. You’ll set the CreateAccount rule to priority 5, so that the DuplicateAccountCheck rule always fires before the CreateAccount rule.
Expand the Declaration section as needed so you can see empty rows below the headings Term and Alias.
Each of the sections can be expanded and contracted as needed.
Drag the Account concept from the TIBCO BusinessEvents® Extreme Studio Explorer tree into the first empty row in the Declarations section. You see the project path of the Account concept in the Term column, and account in the Alias column.
Similarly, drag the Create event into the next available row. Change the event alias to createevent.
Declaration The Declaration provides the scope of the rule. It lists all the entity types to be used in the rule, and their aliases. By default the alias is set to the entity name in lower case letters. You can change it as desired.
In the Conditions panel, type the following:
```
Account.lookupByIdentifier("none", createevent.identifier) != null;	
```
This uses the generated query function for the Account ByIdentifier key. This will return an account with the specified identifier if the account already exists.
In the Actions panel, just below the Conditions panel, type these statements:
```
//
//    Indicate that account already exists
//
System.debugOut("WARNING: Account " 
    + createevent.identifier
    + " already exists.");

//
//    All done
// 
Event.consumeEvent(createevent);
```
These actions are done only if the conditions are met. If not, then the next rule in the agenda fires — and that is the CreateAccount rule, which you’ll define next.
You are also consuming the event, so it cannot trigger any other rules.
Save and close the resource.

Add the CreateAccount Rule

Right click the Rules folder again, and select New > Rule.
You see the New Rule Wizard. In the Rule name field, type CreateAccount.
Click Finish.
In the Form tab, set the Priority field to 5. This is a lower priority than the DuplicateAccountCheck rule.
Drag the Create event from the TIBCO BusinessEvents® Extreme Studio Explorer tree into the first empty row in the Declaration section. Change the alias name to createevent.
This rule has no conditions — the DuplicateAccountCheck rule means there is no need. You could have combined the two rules into one. There are many ways to write rules for a project. You have to use your judgment.
In the Actions panel, you’ll use an ontology function to create the Account concept instance. You access the ontology functions using the function catalog.
From the top menu select Window > Show View > Other > TIBCO BusinessEvents® Extreme > Catalog Functions. The Catalog Functions view displays on the right (unless your Eclipse IDE is configured differently — it could display along the bottom, for example).
Below each concept, event, and rule function is its ontology function. Expand Ontology Functions > FraudDetection > Concepts > Account > Account.

Drag the Account function into the Actions section. You see its signature:

Concepts.Account.Account(
     /*extId String */,
     /*identifier String */,
     /*balance double */,
     /*status String */,
     /*averageMonthlyBalance double */,
     /*recentDebitBalance double */)

Update the function to create the Account concept, and type the rest of the actions as follows. You can double click the tab to expand the rule editor, to make rule writing easier.

//
//    Create a new account
//
Concepts.Account.Account(
   "" /* no external identifier */,
   createevent.identifier,
   createevent.balance,
   "Enabled" /* account is enabled by default */,
   createevent.averageMonthlyBalance,
   0 /* no current debits" */);
   
System.debugOut("INFO: Created account " + createevent.identifier);

//
//    All done
//
Event.consumeEvent(createevent);

Save and close the resource.

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