Workflow permissioning criterias matching

Question

Currently, I have a workflow table quite complex containing multiple values that combine between each others. It is basically a workflow to find the right approver for the right user in permission model Here is a simplified example of workflow table

Country	Department	Role	Approver
ALL	ALL	ALL	Bob
UK	IT	Developper	Tim
US	IT	Developper	Mike
ALL	ALL	Analyst	John

Those workflow steps always follow pre-requisite :

1. It always exist the default approvers with matching ALL criterias
2. Any criteria matching take precedence on the ALL criteria
3. If no criteria match, it will fall inside the default approvers

I have users that need to be approved according to above matrix

User	Country	Department	Role
U1	UK	IT	UX designer
U2	US	HR	Analyst

I am trying to figure out how i can extract the following matching :

User	Approver	Reason
U1	Bob	User U1 does not match the criterias so its climb to the default approver
U2	Tim	User U2 match workflow step because Tim validate all UK Developpers belonging to IT department

Of course for this example there is few criterias so a simple if / else would solve it. But I have 6 criterias which I believe would reach an important number of combinaisons if applying this naive approach.

In this situation, does a rule engine would apply this problem ? (for instance drools?) I would think the engine would take user / and list of workflow step as a fact. Should a decision table more applicable in this situation ? Any help in structuring the problem would be more than appreciated :)

Here is a really simple example of matching a user to its approver country

rule "Has country approver"
when
    $user : User( $country : country )
    $wf : WorkflowStep(country == $country) from $userAccess.steps
then
    //take the approver for the matching step
    $userAccess.setApprover($wf.getApprover());
    
    //insertLogical ?
end

Answer 1

A rule engine is a perfect fit for your solution, you have to decide how to use it though.

The example you provided using Drools directly is very low-level, it works but it'll require you to write the rules in DRL.

Since you already know your evaluation is stateless and your input are literally formatted as a table, a Decision Table would be a better fit in my opinion. Given that you have two flavours of Decision Tables, Drools' and DMN.

I'll suggest you to try with DMN's as it's easier to start, Kogito provides a quick-start that let you experiment with the whole system and even write a test scenario for that, which is basically your second table.