Yesterday we saw the basics how to create a project with the Business Rules Maintenance Web Application and connect the resulting Zip file to a Pentaho PDI transformation.
Today I show you how to write two rules. The transformation starts with a CSV file input step. The file contains data of US airports. We will check two fields of the file which contain information about the airport type and the US State it is located in.
The final result will be a list of rows of airports that are of large size and located in the state of New York.
Below find the screenprints for a step-by-step walkthrough.
The project we created yesterday with the reference to the project file exported from the web application
Modified the transformation to read data from a CSV file, run it through the rule engine and then filter all rows where the number of failed rulegroups is zero - meaning that the rulegroup passed.
A preview on the data from the CSV file. We will write rules for Field_002 (the type of airport) and Field_009 (the US State)
Login to the Business Rules Maintenance Web Application
Click on "Project" to go to the project overview page
Select the project we created the last time - click on the project name
Click to add a rule group.
Enter a name and description for the group. Select a valid from and valid until date for the rule group. Then save it. Finally click the arrow to go back
The rule group we created. If necessary do maintenance of the group from here
Click on the rule group name
On top there is the project and rulegroup info displayed. Rule groups contain one or many subgroups, which group rules together. When a rulegroup is created, a first subgroup is created automatically.
Click to add the first rule
Enter a name and description for the rule. Next enter the exact name of the field (here: "Field_002" - the name of the field from the PDI transformation) and select the data type of the field. Next select which check you want to use (here: CheckIsEqual to check for equality). Next enter the value to check against (here: "large_airport") and select the data type. Next enter a message in case the rule fails and one in case it passes. Placeholders can be used - $0 is the value to check against you entered before ("large_airport") and $1 is the actual value from the CSV file in the transformation. Click on save and then go back.
Click to add another rule
Add another rule like before but for field "Field_009" containing information about the state the airport is located in. We want to check that the airport is in the state "US-NY" (New York). Click on save and go back.
Back to the overview the two rules are visible. The first checks the airport type and the second the state the airport is located in. The subgroup shows, that the rules are connected by an [and] condition. So both must be true for the rule group to pass.
Click on "Export" to export the project
Select the project and generate the Zip file
Select the folder and enter the filename and click on "Save". Use the same folder and filename as yesterday, so you won't need to change the transformation.
Go back to Pentaho PDI. Right-click the last step to get a preview of the data. The data will come from the CSV file, run through the rule engine and all rows that pass the rulegroup we defined (consisting of the two rules: airport type = large_airport AND state= US-NY) will go to the step labeled "Passed Rows".
This is the preview result. It shows all rows having an airport type = large_airport AND state = US-NY. Only 5 rows of about 45000 passed the test. The columns on the right are added to the stream by the rule engine and give you some statistics and results to filter on.
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