# Chemistry documents semantics by Redfield Error **URL:** \ **Category:** Partner Extensions\ **Tags:** other-partner-extensions\ **Created:** [April 29, 2021, 2:11am UTC](https://forum.knime.com/t/chemistry-documents-semantics-by-redfield-error/32611 "2021-04-29T02:11:51Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![rfeigel](https://forum-cdn.knime.com/letter_avatar_proxy/v4/letter/r/7ea924/32.png) [@rfeigel](https://forum.knime.com/u/rfeigel)\ **Post date:** [April 29, 2021, 2:11am UTC](https://forum.knime.com/t/chemistry-documents-semantics-by-redfield-error/32611/1 "2021-04-29T02:11:51Z")
I’m trying to run this workflow and get the following error message: ![Error Message](https://forum-cdn.knime.com/uploads/default/original/3X/c/4/c411f7514aa8f50f932c4b66bf6812b6f9eea99a.jpeg) It occurs in the Document Selector component: ![Document Selector Component](https://forum-cdn.knime.com/uploads/default/original/3X/5/5/5521959e0b61f8a453aea573d0dc091c80c01b9c.jpeg) It appears the problem is in the first Groupby node: ![Groupby Node](https://forum-cdn.knime.com/uploads/default/original/3X/a/c/acff613b35e3c23e112fa60dacbef984afdb72eb.jpeg) Any suggestions? ---
**Author:** ![elsamuel](https://forum-cdn.knime.com/letter_avatar_proxy/v4/letter/e/b4bc9f/32.png) [@elsamuel](https://forum.knime.com/u/elsamuel)\ **Post date:** [April 29, 2021, 7:58am UTC](https://forum.knime.com/t/chemistry-documents-semantics-by-redfield-error/32611/2 "2021-04-29T07:58:55Z")
Are the missing columns present upstream of this component? ---
**Author:** ![rfeigel](https://forum-cdn.knime.com/letter_avatar_proxy/v4/letter/r/7ea924/32.png) [@rfeigel](https://forum.knime.com/u/rfeigel)\ **Post date:** [April 29, 2021, 2:00pm UTC](https://forum.knime.com/t/chemistry-documents-semantics-by-redfield-error/32611/3 "2021-04-29T14:00:09Z")
Sorry. I didn’t realize that I have to make a selection in the NE Selector component. After selection, workflow runs.