I am indexing my a pdfiles from Zotero inside DT database, I noticed that some of the files are corrupted, I have a smart folder with all pdf, is there any possiblity to list all corrupted files through separate smart rule? Unfortunately ther is no rule for content not matching something 
if the content doesnt match “a” it means it is broken,but I dont know how to negate condition in DT
The NOT operator is not implemented after 10 years?
Take a look at page 228ff of the the manual (also available through the in-app Help). Page 229 includes reference to the following boolean search operator:
NOT term: Does not contain
term
Stephen
Is the text layer of these files corrupted, e.g. a conversion to plain text creates garbage, or is there no text layer at all? In the second case a simple Word Count is 0 condition should be sufficient.
Thanks this way the smart folder find those files!
It find also other single files that clear have text (but those number are small enough to go through them manually, the desciption of those files is PDF document, but they are PDF + text)
I apologise, my first post make sense (and this is the reason I posted),
then shouldnt comment on random thread from forum as the feature is evidently implemented,
and the confusion steals the attention from the real issue to which @cgrunenberg responded
No worries! Just pointing out the negation operator to you and any future readers 