# Help needed with openEHR GDL

**Category:** [Task Planning/GDL](https://discourse.openehr.org/c/task-planning-gdl/27)
**Created:** 2021-05-07 15:55 UTC
**Views:** 1377
**Replies:** 4
**URL:** https://discourse.openehr.org/t/help-needed-with-openehr-gdl/1537

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## Post #1 by @Rinke

Hi all,

I'm a Dutch clinical informatics PDEng student. As part of my studies I am currently designing (and hopefully developing) a decision support tool to be used in a healthcare department. 

What I would like to do is to translate a natural language clincal guideline (in the format: if patient had this in the past, then advice this/perform this) into a computer interpretable guideline, which can then be used in a decision support tool. Of course I could just program if-then-else-rules in any language, but I rather use an standardized approach for this, with reusable models, concepts etc. 
During my preliminary research I've read about a few languages (e.g. FHIR clinical reasoning module, Proforma, Asbru etc.)  that could do that, but openEHR (with GDL) appeals to me the most because of it's well-thought-out approach and available tools.

As a start I've been following this guideline: https://gdl-lang.org/the-project/guides-tutorials/gdl2/gdl2-guideline-tutorial-bmi-openehr/ 
I've followed every step and double checked everything, but unfortunately I do not get any Execution results. Does anyone have the same issue or knows what I am doing wrong? See image below and attached guideline file:
![image|690x254](upload://hUY5e8OKYOskrv3ZOLq3uzh6vGV.png)

Additional question:
Once I've this working. What tools could I use to execute the guidelines? Ideally I would integrate this in a Python application, is that possible?

Thanks!

Regards,
Rinke
[Test_BMI.v0.gdl2.json|attachment](upload://rLDNYH32l81HUMtrGoDD8VdV1Td.json) (4.4 KB)

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## Post #2 by @Rinke

I discovered the answer to my first question. TLDR; null values aren't allowed, check for them.

After trying to reupload the guideline file into the gdl2-editor I received the following error message:
![image|431x122](upload://a7CTWeiyilszR4A7DqMmsGUYAE2.png)

After looking at the gdl file it turns out, somehow a predicate with *max(null)* slipped in there, which is not allowed, causing the execution to fail:
![image|681x364](upload://50CFOzlUSg4lWljZbFPiIK8VVmd.png)
Removing the predicate made the execution run succesfully.

Lesson learned: when execution in editor fails look for *null* in the code or try re-loading the GDL 

The latter question remains:
[quote="Rinke, post:1, topic:1537"]
Additional question:
Once I’ve this working. What tools could I use to execute the guidelines? Ideally I would integrate this in a Python application, is that possible?
[/quote]

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## Post #3 by @thomas.beale

[quote="Rinke, post:1, topic:1537"]
During my preliminary research I’ve read about a few languages (e.g. FHIR clinical reasoning module, Proforma, Asbru etc.) that could do that, but openEHR (with GDL) appeals to me the most because of it’s well-thought-out approach and available tools.
[/quote]

For academic purposes, you may want to have a look at the Task Planning and Decision Language (TP/DL) specs, in the [PROC component](https://specifications.openehr.org/releases/PROC/latest). The DL part is emerging, so it's more to look at where we are going in the future. You might find [this discussion](https://discourse.openehr.org/t/dl-vs-gdl2-purpose-and-difference/1485) useful.

GDL is established and deployed, has tools etc, so for doing any real implementations, I'd use that.

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## Post #4 by @Rinke

Thanks for your repsonse Thomas. I'll definitely have a look at it!

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## Post #5 by @Rob

Cool! Ik kwam via via hier uit. Dit project nog steeds up and running?

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**Canonical:** https://discourse.openehr.org/t/help-needed-with-openehr-gdl/1537
**Original content:** https://discourse.openehr.org/t/help-needed-with-openehr-gdl/1537