dmn abs function throws an error

[Ravi Mangalagiri]

Hi Kogito Team,

I have a dmn and also defined a DMN Decision Service called evaluate.

I now imported the above dmn in another dmn and calling the decision service and passing the inputs

dmn1.evaluate(input, amountFromDMN2)

I double confirmed that both the inputs are not null.

The first dmn has a decision which uses the function abs(). and it throws an exception as follows.

The parameter 'duration', in function abs(), cannot be null.

I also tested the first dmn independently and it works just fine. All I have in the decision is abs(input.amount - amountFromDMN2)

The question is when does this error occur?

--

Ravi Mangalagiri

[Ravi Mangalagiri]

I was able to reproduce the error. Please find the attached 2 dmn(s)

payload 

{

    "loan": {

        "insuranceAmount": 5000

    }

}

also noticed the following exception in the console

executed 'loan.dmn' with 2 errors
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.kie.dmn.core.impl.DMNMetadataImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: org.kie.dmn.core.impl.DMNContextImpl["metadata"])

[Matteo Mortari]

Hi Ravi,

your Decision Service "evaluate" in the loanCalc.dmn defines the input parameters as: baseLoanAmount, loan (screenshot attached)

in your invoking loan.dmn model, you are invoking it by having inverted parameters: calc.evaluate(loan, baseLoanAmount) 

(screenshot attached)

If you are invoking positionally, you shall respect the correct order of the Invocable element (the Decision Service, in this case) parameters.

If you respect the correct positional ordering of the parameters during the inline invocation, no error is produced for the example payload reported.

Hope this helps!

MM

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Matteo Mortari

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[Ravi Mangalagiri]

Matteo,

The error is misleading ... and where is this documented? Not sure how I missed it.

Thanks. That fixed it

To view this discussion on the web visit https://groups.google.com/d/msgid/kogito-development/CAHOoiEprqzFGUBpsMc_n2a54qYVqMFqDvnOQ4KsCHQojXEr9vw%40mail.gmail.com.

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Ravi Mangalagiri

[Matteo Mortari]

Hi Ravi,

for the Documentation of the DMN Editor, I will let my colleagues for Tooling advise.

for the Documentation of the built-in functions, we are experimenting to provide a specialized handbook, for instance https://kiegroup.github.io/dmn-feel-handbook/#abs-n

in this case, it's trying to tell you that you have passed a null value to the abs() function as you know it's the result of the expression input.amount - amountFromDMN2

(it likely tried to use number variant first, then duration variants, but still null, hence it's reporting assuming duration).

How that occurred, it's a side effect of what I've described in my previous email.

For an analogy, if you invoke:

isParent( child, johnDoe )

or

isParent( johnDoe, child )

Which one is "the correct" one?

Hard to tell even for humans, it depends on the definition of the function.

For Invocable elements (a Decision Service, in this case) you may opt for a boxed invocation, as that corresponds to named-parameter-invocations, it would avoid this problem altogether.

Even though I personally use inline (positional) invocation a lot of the time, but that need to ensure the positional parameter is indeed the expected one.

Hope this clarifies further.

MM

To view this discussion on the web visit https://groups.google.com/d/msgid/kogito-development/CALg%3DC8OLpvONcWsakYpzBL1k-r%3DL66m5EL9Dynru04VJJfcySA%40mail.gmail.com.

[Jozef Marko]

Regarding UI, there was an initiative of adding some functions documentation directly into editor UI, similar as we have for keyboard shortcuts for DMN or BPMN editor.

However this initiative was stopped due to a changed focus of the team. So there is no detailed documentation directly in editor/tooling of FEEL functions.

In other words, there are no example how to use 'abs' or similar. The autocompletion (should appear automatically when typing dmn literal expresison) just offers list of available functions.

To view this discussion on the web visit https://groups.google.com/d/msgid/kogito-development/CAHOoiEp-k83sUi9TUT%2BrizgidLA03noki%2BS5SHG2rAyHXpqkBQ%40mail.gmail.com.

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Regards, Jozef

RHBA Quality Engineer

[Matteo Mortari]

Just for completeness, specifically about

On Wed, 1 Jun 2022 at 12:56, Jozef Marko <jom...@redhat.com> wrote:

<snip>

In other words, there are no example how to use 'abs' or similar. 

that could be indeed a great situation where to make use of  https://kiegroup.github.io/dmn-feel-handbook/#abs-n

All the examples in there are verified against the latest Drools DMN engine (which includes FEEL engine).

Hope this helps,

MM