Hello,
I tried to execute the KNIME workflow (https://www.knime.com/blog/data-anonymization-in-knime-a-redfield-privacy-extension-walkthrough) for data anonymization implemented by Redfield Privacy Extension. I get this error as I try to execute the 5th node (please see the attached picture):
ERROR Hierarchical Anonymization 0:473 Execute failed: (“NullPointerException”): null
Could you please tell me how I can fix this?
TIA
Sharif
Hello @hello_knime. This bug probably occurs when you provide the anonymization conditions that are not possible to fulfil. I may suggest you to try to make your anonymization requirements a bit loose. One of the most simple way to do that is to set up the suppression limit more than 0. It means that you would allow the algorithm to produce completely anonymized records (with *-values for quasi-identifiers) for some outliers in your data set.
Also you can try to set up a wider range of hierarchy levels in case you restricted them, or maybe you should revise your hierarchies.
Please let me know if this advice is helpful for you, and if it helped to get rid of this error message.
Otherwise please provide more details about the settings that you are using, or maybe you could share a workflow.
Best regards, Artem.
Dear Artem,
Thank you very much for your kind reply. I have tried your suggestion; but unfortunately, I still get the same error (please see the attached screenshot).
Could you please suggest me a list of literature to understand this Hierarchical Anonymization better?
Kind regards,
Sharif
Dear Artem,
Please note that I am simply using Redfield workflow from KNIME. I did not change anything other than supression limit suggested by you.
Kind regards,
Sharif
Hello Sharif. I have just downloaded the workflow and ran it from scratch, and I did not find any issues.
Have you changed settings of any other nodes in the workflow? The Hierarchical Anonymization node might be sensitive to the data set it is processing. Maybe you could share you workflow in an executed state, so I will also have this error as you do?
In order to learn more about hierarchies you can watch the webinar, where I have explained how to work with the anonymization nodes:
You can also refer to the Arx library/application that we used to build these nodes:
https://arx.deidentifier.org/
Best regards,
Artem.
Dear Artem,
Thank you very much for sending me your webinar. I will watch it with keen interest.
Please find the workflow in this link:
https://drive.google.com/file/d/1pvXvO4mViV5hhttTUVuVjHNiVwKkQnr1/view?usp=sharing
I have not changed anything except the suppression limit suggested by you.
Kind regards,
Sharif
Hello Sharif,
I think I have found a found a problem, and it was easy fortunately. Some hierarchies, necessary for the anonymization were missing since you have deleted the connection between Create Hierarchy and Hierarchy Reader nodes. This should solve your problem.
Dear Artem,
Thank you very much! It runs now! Great!
Have a nice day!
Kind regards,
Sharif
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