Evaluate Business Rule - How to retrieve "Collect" Hit Policy output

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1

Hi,
“Evaluate Business Rule” only provide Output from DMN model table’s Output Column, but if DMN model have “Collect” as Hit Policy , how to retrieve List of Results where multiple policy which were got hit are listed?

Currently ,for “Collect” hit policy only “Output” Column from DMN is return with Last hit value.

2

Hello @psupe ,

The activity auto-maps output arguments as scalar types (String, Int32, etc.) based on the DMN column data type. For Collect hit policy, DMN is supposed to return all matched rows as a list, but UiPath’s argument binding resolves to only the last matched value because the output variable type isn’t a collection.

Try this:

Use a List(Of ...) Output Argument

The key is to manually override the output argument type to a list/array in Studio:

  1. In the Evaluate Business Rule activity, go to the Arguments panel.
  2. Find the auto-populated output argument (e.g., OutputDiscount).
  3. Change its type from String → List(Of String) (or the appropriate type).
  4. Assign it to a variable of type List(Of String).

UiPath’s DMN engine does return the full collected list — the problem is the default argument type binding swallows it into a single value.

Thanks,
Karthik

3

I tried it and it doesn’t worked, Attached are errors

543727c3-d194-4735-8542-f85e98849255
543727c3-d194-4735-8542-f85e98849255458×143 14.1 KB

8d1e2fad-92e6-44a7-be99-5853071d14c2
8d1e2fad-92e6-44a7-be99-5853071d14c2369×125 7.87 KB

4

Instead of using the Collect hit policy, try changing it to Unique and adding separate output columns in your DMN table—one column for each result you want to get back.

For example, instead of having one Audit_Result column return multiple values, use Audit_Result_1, Audit_Result_2, Audit_Result_3 — each returning a single value, so there are no issues with the activity.

Then, in Studio, just put them together into a list yourself.

And if some columns come back empty (because not every rule fires every time), clean them up. It’s a bit of a manual workaround.

Also, could you share your DMN file? If I can see how your table is set up right now — the columns, rules, and hit policy — I can give you a much clearer answer instead of speaking generally. Just export it from your DMN editor and drop it here.

Thanks,
Karthik

5

Interesting Workaround though not ideal.

I will use for now in my project. Thanks

Can’t upload actual DMN due to restriction. but you can compare it with attached image.

Screenshot 2026-03-11 143852
Screenshot 2026-03-11 1438521038×684 134 KB

6

Hello @psupe,

I tried calling the business rule and here are my findings:

image
image556×282 21 KB

I can see two matching groups with traces, and I also checked the API to see if we can trace through it, but nothing appeared in the API documentation.

If you have a limited number of groups, then you can define the DMN similar to the example below:

image
image1249×545 31.7 KB

However, this is not a scalable approach.

Thanks,
Karthik